I believe that coalition building is, a bit like improv comedy, very much a "yes, and" kind of approach. If Harris agrees with these policies then there's no reason she can't also quote-retweet and say "I agree" and then this isn't actually a fight.
This is exchange only becomes a fight if one of them doesn't support those things. Is it a fight?
Maybe Harris herself stands for these things (I doubt it given how she's worked to criminalize effects of poverty as DA, frankly) but it really does show how toxic her supporters are that they can't read this as a good-faith attempt to build from where she's starting.
Because Brie is implying Harris is against those things at the jump.
Just jumping out of a bush in public and screaming "You're pro cancer!" At her would the same effect more or less.
I wouldn't respond to it either.