Asexual Attitudes Towards Sex and Why They're Relevant to Fetishes, Kinks and BDSM
Asexuals don't feel sexual attraction to people. That means that the biggest draw to sex for most people is completely absent for asexuals.
But that doesn't mean that all asexuals hate sex. In fact, it opens up room for a wide range of reactions to sex, many of which have been given labels.
Sex-repulsed asexuals (also known as apothisexuals) find sex gross, scary, or otherwise extremely unpleasant. Some apothisexuals are fine with sex being discussed or even with watching porn, but draw the line at actually doing anything sexual themselves. Others find that various degrees of exposure to other people having sex (ranging from viewing porn, viewing scenes that hint at sex, hearing people describe sex, engaging in academic discussions of sex, etc) also bother them. And many are in between - personally, I'm a sex-repulsed ace who is fine with academic discussions of sex, have varying reactions to descriptions of sex and to viewing scenes that hint at sex, and am consistently grossed out by porn.
Sex-indifferent asexuals have an essentially neutral reaction to sex. Generally, they describe sex as boring, pointless, or tedious, but not actually repulsive. Essentially, the same way I feel about washing dishes (assuming the sink is reasonably clean). It doesn't bother me, I don't find it upsetting, but there's really nothing appealing about it, and I'll only do it if I have a good reason to.
Sex-favourable asexuals, on the other hand, find sex enjoyable. Even though they don't feel an innate draw towards sex, they might find sex fun because of the sensations, the physical closeness, their partner's reaction, or other reasons. Essentially, they like sex for non-sexual reasons. Some sex-favourable aces find sex an amusing pasttime, but not something they need to actively seek out. Other sex-favourable aces want to actively seek out sex for non-sexual reasons (this latter group are called cupiosexuals).
Why is this relevant to fetishists and kinksters? Because people who aren't turned on by your fetish or kink can show the exact same range of responses.
People who seek out kink for non-sexual reasons ('cupio-kinky', if you wish) often identify as kinksters themselves. I have heard from a number of BDSM practitioners who say that BDSM is completely non-sexual for them, that it appeals to them on an entirely different level. There are also people in many fetish communities who are motivated by non-sexual factors, such as ABDLs who wear diapers for comfort or security rather than arousal, or crossdressers who like the feel or aesthetic of the outfits instead of being turned on by them.
Other people don't actively seek out a kink or fetish activity, but find it enjoyable nonetheless if it comes up. Often it only comes up because they have a kinky partner. This woman who dated a foot fetishist, for example, is like the foot fetish equivalent of a sex-favourable ace. Feet do nothing for her, but she seems to have enjoyed doing foot-related stuff with her partner.
There are also people who are meh about a fetish/kink. With regards to feet, this is where I'd fall. I don't really care if I can see someone's feet or if they see mine. And if someone wanted to give me a foot massage, my reaction would be just as meh. (I wouldn't want to do a foot job or have my foot licked, but those are more extensions of me being repulsed by sex and other people's saliva rather than anything foot-specific.)
And then there are the people who are repulsed by a fetish or kink. They might be OK with discussions of the fetish, but have strong negative feelings about the idea of engaging in it themselves. (This is how I feel about being a bondage bottom - it would be absolutely terrifying for me, but I don't mind hearing others talk about it.) Or they might find that even mentioning it really bothers them. (Scat play is this for me. Ugh.)
If you have a fetish or kink yourself, keep in mind that the people you discuss your fetish with could fall anywhere on this spectrum. And it's important to respect the needs of people anywhere on this spectrum, especially if you're in a relationship with them.
For someone who is repulsed by your fetish, it's important that you respect their limits and refrain from trying to involve them in your fetish. Make sure you know what their limits are - maybe the fetish not be discussed unless absolutely necessary, maybe it's OK to discuss the fetish as long as you don't expect them to engage in it with you, or anywhere in between. Know their limits and respect them. You don't have the right to force someone else to be involved in your fetish.
If you're in a relationship with a person who's repulsed by your fetish, you need to accept that most likely, your fetish will never be a part of that relationship. You'll either have to meet your fetish needs elsewhere, suppress your fetish, or end the relationship. Just like an allosexual involved with a sex-repulsed asexual, your sexual needs are not going to be met by that person. Don't expect that you can 'turn' them - better to assume it's not going to happen.
If the person is indifferent to your fetish, then you can probably safely discuss it with them, as long as you keep in mind that fetish-related discussions will almost certainly be far more interesting for you than for them. If you're in a relationship with them, you might be able to talk them into doing a fetish activity, but remember that you're getting way more out of it than they are. You should be willing to do stuff that they enjoy, too, sometimes. This might be vanilla sex, or a different kink that you're not interested in, or something else entirely. But if you're getting way more out of the relationship than they are, the relationship will not function very well. And again, if your fetish does nothing for them, then you probably won't be able to turn them.
If the person is favourable to your fetish, great! But do keep in mind that they might not want the same things out of it as you do, or may not enjoy it quite as much as you do. In addition, some people who strongly like something for non-sexual reasons will still find it gross or unpleasant if you mix sex with it (for example, my brother is a Pokemon fan, but Pokemon porn squicks him out). Even if they like that thing, and they like sex, they might not like both together, just like you might not like steak with icing on top. (Although I probably would enjoy that!) As with the indifferent folks, if you have someone who likes your fetish less intensely than you, you need to consider doing the stuff they enjoy more, too.
Overall, remember that everyone has different likes and dislikes, and just because something is amazingly exciting and awesome to you doesn't mean that everyone else will like it if they only give it a chance. This is true for everything, including fetishes.