Because he's socially awkward??
I thought that was rather obvious...
Yeah, but yaoi-logic aside, in the real world forcing a complete stranger to blow you would not just be awkward, but the fastest way to get that person to absolutely despise you.
It has nothing to do with yaoi-logic. There actually are people who blurt out different things from what they meant to say due to their immense social awkwardness.
And it does not necessarily end up in being hated. It always depends on the two people in question (relationship and personalities), sometimes their sexual interest, as well as the cirumstances of the person being asked. It's likely the other person will dislike/hate you, but it's not a given.
Why didn't you tell him to go out with you? Stupid