Well, the leverage is that some profit is better than no profit, in theory.

Assuming that you don't then become locked into mandatory "agreements" (and I use the term loosely given the inability to refuse) with rates that keep going up. Leaving aside that sometimes the principle outweighs the profits; a link tax, or any other restriction on linking, is an abhorrent constraint on the Internet.

If FB and Google both leave Brazil, it will put pressure on the lawmakers to rescind the law.

Yep true, it's a game of chicken really. This is probably what will happen in Canada anyway