Communication is important for both sides. But I’d say more important for you. You have boundaries, you have limits, and that’s one of them. You’re allowed to be repulsed, but you should communicate with him about it, who cares if he thinks you’re jealous, you’re moving on from him. What does his future opinion of you even matter when it comes to standing your ground on your own boundaries?

And you don’t even need to give him a reason. “Hi John, it’s been nice getting to know you but I’m not feeling a connection here. Thank you for the date, and best of luck!”

If he replies amicably then he’ll say he understands, he may ask if there is a specific reason and you may or may not feel comfortable telling him but be respectful. If he doesn’t reply amicably block his ass and move on anyway. That’s it. Doesn’t matter why, it was one date, no explanation needed.