Ignoring it is always an option. As is keeping an open mind, standing by your principles, and joining the discussion. You have a lot of options available. To name just a few: You don't have to read it, you don't have to respond to it, if you do throw your two cents in you don't have to respond to any of the replies. You're under no obligations.
Social discussions are based on a tenuous unwritten & unspoken contract of mutual participation. And with the tendency for political bullying over the past few years, I'm inclined to not participate. If you don't feel an overwhelming compulsion to set people straight I'd just leave it alone. I think the idiom "let sleeping dogs lie" is applicable here.
I don't do FB, but I suspect if it is your wall, you should be able to remove the comments.
I'm coming to realize that we're all messed up. The choice to play victim or not--to take control & responsibility--is the only bit fully within our control. I don't know for sure, but I suspect you're dealing with someone who has the victim mentality, and is comfortable in their adopted role. It's scary to take responsibility and figure out how it all works.