As in all parameters of human behaviour, there are a small number of aggressive/ violent mean and women, but from what I e studied the 1 in 100 most aggressive person in a room will ALWAYS be male.
A few ideas as a bloke, why this may be. First evolutionary speaking, we are pretty much highly evolved apes, shows of physical strength or dominance would have been advantageous during the 10s of thousands of years our species spent as hunter gatherers in small groups fighting and raiding each other, more aggression equals more food and more prestige in a group. If you look for example if you Google 'moriori genocide' you will see what happened when this group encountered the well known Maori, the former practiced a none violent cultural norm, but when the Moari arrived on the Chatham Archipelago, and nearly completely wiped out this group. We can see in this case that cultural values of peacefulness were destroyed by that of violence, and so from an evolutionary point of view, being extremely violent was until very recently (this was in 1835) critical to survival.
I personally have been I a few situations where some drunk was clearly looking for a fight (I think the previous points of why some men do this, typically around social displays of trying to be strong have merit), but, I didn't get out of this situation by being nice, or fighting him, instead I had to make it look like I'd do him far more physical harm than he would do me. I think this is very common especially when discussing male on male spontaneous violence with strangers, its often fuelled by alcohol, which actually makes you more aggressive, and is often done to signal that the individual is more dominant, literally like a couple of chimps squaring up to each other, which is a bit depressing when you think of it like that!
I honestly don't know how you prevent incidents like this. It doesn't matter what I, or anyone else says, of a predator or bully wishes to do harm, then I'm not sure you can prevent this, they simply don't care about the moral or civil reasons for doing so. In relation to whether testosterone has something to do, I'd definitely agree, if you examine the reports of women who started taking the hormone they noted it made them feel more confident. I play rugby, amd in that context there is definitely a rush you get when playing, and it's absolutely tapping in to the ape part of our brains that enjoy this. Not an optimistic post, but i do sadly think its the reality!