I can see this, yes and no. On one hand, I sort of had those feelings when my wife and I started fucking around together. But they quickly went away with the feeling that "it's not gay if a woman is there.' So I easily started kissing/eating my wife or his wife after she sucked off/was fucked by another guy, did DP, did DVP. Since the guys butt fuck our wives and each others wives, the guys sometimes now do it to each other. So it evolves as time goes on, as it always does.
And yeah, so on the other hand, if most guys are sure homophobes, then why is MFM so popular over FMF? If two guys are doing it to one woman there's go to be some ball knocking and friendly fire expected.