Many of the things PETA does (and, tellingly, what they don't do) seem to give the lie to their stated aims. If my goal were to reduce meat consumption, I'd be trying to partner with communities to help build gardening practices and such. Instead they invest heavily in grandstanding, which seems more aligned to jerking selfrighteously than actually effecting change.
edit: I stand corrected that PETA are generally much more extreme than the RSPCA
PETA takes the position that animals are better dead than kept as pets, and because of that they don't merely kill many animals given to them, they've been known ro actively take adoptable animals from shelters to kill them.
The RSPCA do have issues. Yet they remain important protectors of animal welfare. They also arguably predate our police forces as we'd know them today.