Should I come out as asexual?
Generally speaking if you're comfortable with doing so, yes. Disclosing your experience with others creates a deeper bond between you, frees you from guilt and stress, and can even help you to understand yourself. Letting a person know you're asexual takes it from an idea in your head out into the real world, better allowing you to come to terms with it and move on from there. Of course, it also makes sense to come out in situations where you orientation will be relevant, such as to a romantic partner.
That said, you don't need to come out, and if you don't feel safe – or even if you just don't want to – then it's best not to. Though asexuals aren't often victims of hate, when people are ignorant they can say some hurtful and invalidating things. If you are reliant on the person you are coming out to (e.g. a parent), then it might be best to wait until you aren't. At the same time, often aphobia comes from a place of ignorance, and educating others can help a lot. Perhaps you could get them to read websites/articles such as this one.
Ultimately whether you want to come out or not is entirely up to you. You can find some quotes from asexuals that have come out in Experiences: Coming out.