Bro is associated with obnoxious, stupid, despicable, disrespectful.
Which, for "bro", is fine by me.
The real problem is that 'bro' is inherently masculine in a male-dominated industry - which has unfortunate implications if we're trying to be inclusive of women. That's it. If people use it enough as a technical term for a piece of software, maybe 'bro' - like 'man' - will stop feeling weird when you type it into the command line.
Until then, it absolutely is offensive and unwelcoming.
This sounds a hell of a lot more like an issue with you vs an issue with the term. When I think of 'bro', I think of the short form of calling someone brother endearingly. I wasn't even aware of the frat context until a few years ago. Hell, even within the frat context, it's not necessary "obvnoxious, stupid, despicable, disrespectful", it's just a young guy who's part of the party culture that's associated with college, at least in the US.