The least fun thing about straight cis folk giving you queerphobic lectures is that it forces you to become one of two people:
1) The uptight minority who contradicts them, possibly leading to a fight that makes the whole situation awkward and uncomfortable
2) Someone who swallows their feelings, stays silent, and hates themselves for it afterwards
The first will wind up giving you a reputation as difficult, the second an ulcer. Neither feels like winning.