Because there is nothing wrong with the word "bro".
Denotatively, it's meaningless. Connotatively, it's turned into a pretty objectionable term, in my opinion.
Somebody has invented drama around this word, some other people have bought into it, and now more people are just trying to stir it up again because Hacker News has somehow gone a whole two days without senseless bickering.
That's not how 'connotation' works.
I choose the former.