If anyone touches you in ways you find inappropriate, you tell them to stop, regardless of whether they are straight or gay. Otherwise, don’t treat him any differently than you would your straight friends and be a witness to God for him.
I have bisexual tendencies. I choose chastity. My girl friends (including my roommate) know and they don’t treat me any differently. To them, I’m still like a sister to them and their opinion hasn’t changed. They support me in my walk to chastity. One of them, a very good Catholic, told me, “Hon, you’re called to chastity, just like I am and it’s a difficult struggle for all of us, but we can help each other.” My openly gay friends respect me for standing for what I believe in and for treating them like people, while knowing I disapprove of their lifestyle. One of my Catholic guy friends reminds me that I’m still worthy to be loved by a good guy (should God hold that for me), still a beautiful person, and his opinion of me (a high one) has not and will not change. My priest is very helpful to all of us with chastity (he works on two college campuses, so he probably has to be, lol).
I choose to be open about it because I want to show other people it’s still possible to be chaste and a good Catholic. Also, because I hope my struggle can help someone else.
I’d be really sad if people were told not to associate with me because of this. I believe Jesus would love them and show them how to be chaste, saying “Go and sin no more,” like He did with the woman who would have been stoned for adultery. I think, more than ever, they need to know that they are loved by God, that He alone can fulfill them, and that we accept people for who they are and that we should help all Catholics live a good Catholic life, while showing others how much Jesus really loves us.