To simplify even more from a general anthropological perspective of many topics...

Tribalism is a reault of conservative values no matter how ethically good the cause or what those values may be. Not adapting to what's socially going on, or doing things like responding to an oppressing tribe by using the same tactics of that tribe just creates discord. One need simply compare MLK to the Panthers. Same cause at the core, but entirely different values and ideology. And of course, tribalism is rife when there's in-fighting of those that are ultimately wanting the same core outcome because it's deteriorated to camp vs camp.

Lastly and most importantly, it gives bad reputation to the core idea and creates social opportunity to instill doubt with fallacy...

"They champion for this. It's good."

"Yes. But they also do this, so it cannot be good."

"This is true."

It's not, but the average of our collective doesn't think hard enough to consider such things. We fucking love a good flag and warcry; tribalism is in our nature and an old lingering detrimental trait that even the most progressive of intents can be snuffed out or tarnished by.

I don't know the full details of the BP demise, but I imagine this general recipe we see countlessly in all history is not too far off.