I'm confused by a few things. First, why "compare?" Usually that indicates a contest of sorts - with either the larger or smaller being the "winner." Is that the point? And who wins?
Second, someone described jerking off together as a non-sexual encounter. Are you serious? Jerking off together, no matter how you define yourself, no matter with whom you are masturbating, is by its very nature sexual. Random boner in the presence of others? Not necessarily sexual. Stroking said boner? SEX. Stroking someone else's boner...DEFINITELY sex.
Third, as such, I can't believe "straight" (quotes to emphasize category) men would ever have the opportunity to compare their erect units in a "non-sexual" atmosphere, (nor the interest). For that matter, neither would gay guys. Unless you can seriously imagine two or more guys, with boners, eruditely examining each other with medical dispassion simply because there was nothing better to do to pass the time...
"Say James, I was just lounging here groggily in a 115 degree sauna, giving my stiffy some time to air out, and apropos of nothing, but I noticed your cream pipe looks to be a smidge over 7.8 inches, is that about right? I'm kind of a savant when it comes to turgid stonker estimation. It's a hobby of mine. No homo."
"Oh ho, you scamp! You must be looking at my chubbed pud in a sideview mirror, my friend, where things are actually larger than they appear to you. My blue vein cigar is at least 8.5" if I'm a centimeter. No homo."
"Damn the luck, wouldn't you know, I left my straight-boner calipers in my other gym bag. I guess we'll have to agree to disagree."
"Hey ho fellows! There's only one way to settle this. Why don't you both scoot those sweaty meat sticks over here near me? My engorged, but totally non-sexually aroused peen is conveniently tattooed with a Department of Weights and Measures-approved scale. And as I am, as you can see, a fabled, and very GIRLFRIEND-pleasing 9.2 inches, I can easily compare your two chowder howitzers to my crotch rocket, and we can put this issue, excuse the phrase, to bed! No homo, of course!"
"Of course!"
"Jolly good!"
"Here here!"
Comparing continues for many, many minutes, with absolutely no touching or sexual subtext, yet miraculously, all three erections remain steely and proud.
"Well, I'll be damned, Tessa, my STRAIGHT girlfriend (no homo), must have used the AOL ruler on me last time. My throbber is clearly only 7.8 inches, just as you had ascertained when you were clinically staring at my uselessly-in-this-situation-hard johnson before, bro. Your powers of no-homo chode observation are uncanny indeed! However did you know?"
"Years of thoroughly non-sexual flesh-flute comparison gives one a very particular set of skills, you know?"
"Remarkable! From now on, what say, we'll call you the Shaft Whisperer!"
"I'm platonicly honored."
"Well, now that that's settled in a totally-non-sexual way, how about those Dodgers?"
"Indeed!"
Uh huh. Just get over the incredibly antediluvian idea that "this is gay," "that is gay," and whatever value judgement goes along with that. Just BE. And be happy. Compare, fondle, rub 'em together and start a fire. Nobody cares about categories anymore guys, so stop hiding behind splitting hairs (It's not sex, we're just comparing!! It's not sex, we're just jerking off!" I'm straight but I love to suck cock!") and just enjoy life.