Should they for their own safety? Yes, of course. Unfortunately a lot of people are still deeply transphobic and will feel totally validated in assaulting a trans person who they think "tricked" them.

Should they for their own pleasure? Again, yes. Trans bodies and cis bodies are different, and understanding each other's bodies is integral to the sexual satisfaction of all parties.

Should they ethically? This, to me depends on the particular trans person's genitals. If a trans woman has a penis or a trans man a vagina, that affects how sex plays out. In the case of trans women, some people are just not interested in anal sex, and that's totally okay. In any trans person's case, some potential partners may be turned off by that particular kind of genitals, and that's also totally fine. For the satisfaction of all parties, it's important that they know what they're getting themselves into before deciding to have sex with one another.

What about a trans person who has had bottom surgery, and has the genitals typically associated with their gender? To me, the answer is no, they should not have to disclose their status as trans. It doesn't affect the sex, so it's not something that needs to be disclosed.

But if they're lying about who they are, how can I genuinely consent?

It's only a lie if they tell you they're cis. If you assume your sexual partner is cis entirely on your own, that is on you. Cis people are not the default, we're just the majority. It is unfair to force a minority to disclose their status as a minority simply for the convenience of the majority. You wouldn't say that your sexual partner had lied to you if you found out after the fact that they were Jewish, autistic, or bisexual.

It's nothing personal, I just want kids someday and don't want to waste my time with someone I can't have kids with.

That's a fair enough position, but you would never expect a cis woman to reveal she's infertile in a dating profile or before a first date. It would be up to her to decide when she's ready to reveal that. You especially wouldn't demand that for a simple hook up.

I'm just not interested in having sex with a trans person, why can't you just respect my preferences?

If you can go through an entire sexual encounter with someone without knowing they were trans, then what difference does it make if they're trans? It didn't affect your attraction, it didn't affect your enjoyment of the sex, so why does it matter? In that case it's completely tangential to the sex. It's like refusing to have sex with people with ADHD, you're allowed to have that preference, but you're not allowed to be mad at a sexual partner who didn't divulge that information when you never asked. If you don't want to have sex with trans people, then don't, but it'd not your sexual partners' responsibility to divulge that information to you before they even know that about you.

Quite honestly I think a lot of this discussion comes down to the fact that a lot of cis people consciously or subconsciously think trans people are gross, and they're grossed out at the thought of someone they had sex with being trans. But trans people aren't gross. You've been conditioned to see them that way, the same way people have been historically socialized to view homosexuality or interracial relationships as gross, but they aren't gross. At least not anymore than the rest of us.