The police wasn't as militarized. SWAT didn't exist in its current form back then. SWAT was slowly developing as a domestic counterinsurgency apparatus after the Watts riots. One of the first real assignments of LAPD's SWAT was in fact engaging in a shootout with the LA branch of the BPP.
Even at their most militant, the BPP were mostly armed with pistols and shotguns. Those weapons wouldn't do shit vs your average ICE goon wearing body armor and carrying assault rifles.
