I would call this dubious consent, yes. Rodney never said no (except for at the anal sex) and he had plenty of opportunities to put a stop to things, but he was ambivalent about doing this. Though the physical sex wasn't so much a problem as the Big Gay question. There's no doubt that John was no knight in shining armor here, even if he did believe (possibly rightly) that Rodney needed this as much as he did.

he's getting to his freak out because John got laid and is therefore not pushing and distracting and rationalizing him to stay.

Yep.

I hate to say it, but John didn't want to talk it out and run the risk of Rodney saying no. It's an ego-thing. He was turned down by Elizabeth and it stung. He couldn't take the idea of also being turned down by Rodney. Particularly when a large part of why he asked Rodney was to get his confidence back up.

This may not make sense but, there was a part in the back of John's mind that was convinced that if Rodney said no, he'd "lose momentum" and not get laid at all -- with anyone. It's irrational, but that fear was lurking.

Icarus