Yeah, I think that quote is mixing up causation and correlation. Obesity rates have been rising for the past few decades, mostly linked to processed foods containing higher calories becoming more common, but there's not a jump due to fat activism.

I do think that there are some fat activists go too far. Like, no, you aren't entitled to have hot people be attracted to you, no one's entitled to any attraction at all. However, going out of your way to be a dick to them doesn't help, just like you aren't bullying someone out of inceldom.