I can totally imagine that (what you've quoted his mum as saying).
The problem is that the military, despite whatever they want to tell the public, isn't always so accepting. I'm sure there are some guys in the military who couldn't care less what the sexual orientation is of the guys in their team, it's how they do their job that matters. But not everyone will feel that way, and it might make someone want to keep it quiet on base.
With his mum's words, Corrie probably isn't gay or bi, because she lives far from base and she's clearly got no negative judgment of such a thing in her, and she will have shared that to his brothers, so his family, at least, would be a safe place to come out, even if he couldn't do that while he was on base.
So, if Corrie had accepted a lift from a male who predates on men, Corrie would have probably not gone to be a willing participant, he would have to think it was just a simple lift.
Going by what people are saying about Corrie's 'presence' there's nothing to suggest that he's a problem individual. The worst he would be likely to do on a night out that might annoy someone is perhaps to get off with a girl that someone else has his eye on? That isn't going to lead to Corrie's disappearance...that would be more like a fist fight behind the club.
Honestly, if a female had disappeared like this, I think we'd be pretty certain in our minds that she'd likely been abducted by a man for sexual reasons.
What happens in male abductions, disappearances, murders? Do we have any cases for comparison that don't include sex as a motivator?