FWIW here are some screen caps from youtube at the time of the hit
The first one is right as the ball is hitting Posey's glove. As you can see he is inside the foul lines, and Cousins is already loading up for running him the fuck over....not just loading for impact....even though he has plenty of room to slide around him.
This one you can see Posey is still on the fair side of the lines, but still more in front of the plate. However, there is still room for Cousins to slide around. Oh, and the ball is under Posey and clearly visibile. To say he shouldn't be blocking the plate without the ball is moronic in this case. Before you pull the "He shouldn't block the plate without the ball in the glove" crap - as someone who was a catcher in baseball for 13 years and was in plenty of situations like this (taking the hit and having the other player slide) it is pretty damn tough to focus on getting a good block, prepping for the hit, and making sure the ball is in your glove all within a split second - and most times it's tough to tell if the ball is in your glove.
Oh, and there is the fact that Cousins looks prepped to run through a rebar enforced cement wall. He isn't aiming at the plate to be safe, he is aimed at some fucked up angle in front of the plate, straight at Posey.
I'm not going to go as far as the Giant GM, however, the hit was completely unneeded.
If you think blocking the plate in May isn't needed, neither is loading up and running through the catcher like that.