Since I was a kid, I failed so hard at being a guy. I've always been hopeless at athletics. My body type has always been pretty meek (let me not doxx myself and say more). I hate any sort of competitive environment. I can't hold my liquor for shit. I have a very high pitched voice and an expressive way of talking. Friends have described my voice as a "gay twang". My mum probably assumed that I was gay from day one, as I got a lot of "it's OK to be gay" from her growing up. Sadly I had too much soy or not enough soy, because I grew up attracted to women.
Maybe you old comrades remember, but schools in the 90s were full of homophobia. "That's so gay" criticised any action that deviated from some masculine ideal. I got this multiple times a day, and I learned to stifle my personality to avoid the rebuke of my male non-friends. I'm not even complaining, there's so so many that had it way worse than I did.
Nowadays it's great being a flamboyant straight dude. I can be as sweet, as empathetic, and as expressive as I want. I have cute and colourful clothing. I get really ecstatic around animals. I cry. People like me for being fun and engaged with stuff. Nowadays if some guy colleague says that's "gay" it's like 
"are you alright mate??"
I did go some LGBT events and actions in the past, but not a lot. If I do anything positive, it's to enforce no homophobic language with my students, which guys has gotten a lot easier in the past 20 years. Really, the kids nowadays are much better than we were. OK, I have hooked up with a few dudes here and there, but it feels like stolen valour to call myself bi.
So thanks a whole lot to all the queer people who have made my life much easier, when I've done so little.
Definitely not bi, no sirree
give em a few years mate
or just let him be who he says he is
didn't say i wouldn't
Policing people's labels is kinda intrusive behavior, part of a larger struggle to maintain control over the sexuality and gender expression of others. The cishetnormative patriarchal matrix has indoctrinated us to mark each other in this way, to confine each other to restricitve little boxes that limit our freedom to just be and explore things. We should all strive towards cutting such reflexes out and create an environment where people can live self-determined lifes, and a huge part of that is to claim control over how to express and describe our experiences. Part of that is to not gatekeep bisexuality, but the same goes for gatekeeping straightness.
When you look at how our society treats men who've made the tiniest amount of same-sex experiences as automatically not straight, how guys only get the right to call themselves straight when they've never tested that theory, when male bisexuality is viewed as a "highway to gay", when there's gatekeepy bs like gold star lesbianism etc. etc., it should become understandable where i'm coming from.
Not even saying this guy can't identify as straight, I just went through the exact same thoughts of "stolen valor" when I figured out I was bi in the past year.