I think perhaps the usage has split, with dual meanings, depending on the social identity of the user.
It is still often used by many people for friends (like the quote in the link), with the original meaning.
Some people also use it as a pejorative, usually against people they don't know or like.
I think it is an error to think that the second usage the only one, or even the predominant connotation. I would guess a small portion of english speakers hold negative opinions about "bros", and the concept isn't even on most people's radar.
How often does the word bro get used, and in which context? I would guess that bros use the word in the positive sense more often than other people spend talking talking about bros in a negative sense.
If someone claims that there is only one meaning of bro and that it is negative, I think that reflects more on their social bubble and social leanings than reality.
But it ceased being used that way a while ago. Now, it's largely used to indicate a certain personality type (at least in my neck of the woods).