I hate Facebook as much as anyone here on HN, but the enemy of my enemy is my friend. If keeping end-to-end-encryption also happens to be in the interest of some faceless multinational corporation, we can use their resources in this fight. We can go back to fighting Facebook once this is over.
I don't want to get into who's your enemy and your enemy's enemy and why, but in general the enemy of you enemy is only the enemy of your enemy. It can be your enemy too.
Lighthearted example: any competitive game between 3 or more players. There might be occasional alliances but everybody is the enemy of everybody else.