I don't think we're typically afraid of each other in the same way a woman might be. It's just more about ego, sexuality, and fragile masculinity.
The relationships become difficult to maintain sometimes because we often need to out "man" each other.
The relationships are hard to form because first off there needs to be an equilibrium. They might butt heads a lot if they both want to be "above" the other. And then it has to happen in a very natural, effortless way, since any effort to intentionally try to befriend another man will be met with suspicions of homosexuality.
It's all pretty dumb, but I guess both genders (and therefore all people) have these weird dynamics they need to navigate.