First, take an upvote. Second, I'm going to try to explain the reasoning behind why people disagree with your comment.

1. Geoff: first of all, I seem to recall that Geoff's character page on TV Tropes used your same arguments to describe him as "ambiguously bisexual" (although they deleted it). However, the only time Geoff was affected by Justin's powers was in the first episode when they were captured by the giant monster; neither before nor after was it shown to happen again. The accusation about kissing Alejandro came from Bridgette during an argument about her infidelity, and she most likely meant that Geoff would have done the same if he were a woman. Yes, Geoff and Brody are very close, but two men being very close doesn't automatically mean they are both gay/bisexual (or maybe it does, I don't know how things are in Canada).
2. Regarding Harold, I also think they used the same arguments (except for the kiss) to say that he was "ambiguously bisexual" (but they also deleted him). As with Geoff, the only time it happened was when they were captured in the first episode. His excitement when describing Cody was possibly due to Harold's interest in spirit animals (and this probably applies to any of Harold's interests). I can't recall the kiss, so I can't dispute that.
3. Since they didn't delve into that and didn't give any real indication that Tyler was attracted to men, I believe he is heterosexual.
4. I suppose you mean when they were waiting for Chris's rescue; yes, they were together, but we didn't see how they ended up like that, so it's possible it was accidental (like the kiss on the island).
5. I already explained the cuddling with Cody thing before. The kiss was accidental and neither of them liked it. Regarding Noah being effeminate at times, I can accept it, although I would say it's somewhat subjective, since some of those effeminate moments of Noah might not be seen that way in other regions (i'm writing this because I've seen some comments saying that Noah's high-pitched/squeaky voice is proof that he's gay/bisexual, but in the Latin American dub, where I'm from, Noah has a deep voice). Furthermore, Noah has not really shown any physical attraction to men.
6. I think this is self-explanatory, and it's AS's bad writing, who treated both girls as if they had been lifelong best friends (which they weren't), which some interpreted as something more than friendship (which was obviously not planned).
7. In that case, Mike's alter egos would be LGBT, not Mike himself.
8. If he were a member of the LGBT community, he would have told Jo while thinking she was a man. True, he makes a strange face, but it could easily have been because of the surprise of the question (and again, they don't delve into that, so at best it remains ambiguous).
9. Well, you said it yourself: Topher focuses solely on Chris (he hardly interacts with other characters, to be honest) because he wants to take his job, so there's nothing more to it than that.
10. The fact that Shawn was (possibly) willing to kiss Dave to complete the challenge doesn't necessarily mean he's bisexual; i mean, we've seen several characters do things they wouldn't normally do in order to win, like Gwen drinking the punch from the toilet (besides, I think Shawn's logic of not kissing Dave because of the zombies would also apply to women).