Sorry mate. IMO this is really bread and butter for a team leader.
You're not children. You don't need to be "nice" or "mean".
- hey guy
- I'm really enjoying working with you. You seem to be amazing at x. I'm really hoping I can learn about y from you.
- If I'm really honest though, I just can't concentrate with the fart noises. I know it's just a joke and maybe others are ok with it but it really disrupts my flow, every time.
- Anyhow, how have you been going with z.
Sorry mate this is just wrong all the way up and down.
Don't try diagnosing a co-worker, don't go running to HR asking about "equality" for someone you've diagnosed, and as a team leader just separating yourself from your team is not a solution.