0.5% puts in context that if a small drop in facebook usage would make the political ads a net negative. Just 1% of users dropping facebook in protest, or a small percentage of users reducing their usage because of fatigue from politica adverts would make political adverts not worth the cost. The tiny share of revenue for political ads is going to jeopardise the massive majority of revenue.

The real underlying issue we need to address is that it's nothing to do with revenue. Facebook has a political position that nothing may be out of bounds for facebook. Facebook must be everywhere, everything must be on facebook and that must be acheived at all costs. It's an obviously morally repugnant position, but nonetheless, it's not being challenged.