I was absolutely in favor of opposing funeral protests when they were happening in America[1]. Freedom to protest doesn't mean the freedom to abuse people when they're in an emotionally fragile state. I think it's perfectly fair to have a discussion about the validity of the monarchy moving forward - and I think it's also perfectly fair to let those folks who had some emotional connection (whether reciprocated or single-directional) attend a funeral to remember the queen in peace.

1. https://www.chicagotribune.com/news/ct-xpm-2006-04-20-060420... - the government didn't directly step in in this case but the protestors were effectively silenced by way to crowds of decent folks with loud motorcycles.