I have an idea about why they'd come to a weird conclusion like that:
A "hot" topic like that might have outsized participation. That is, a single post about the topic may have a huge number of comments compared to an every day post. They don't have methodology to differentiate between a rare-but-popular topic and an "every day" topic.
Just another example of how their poor methodology allows poor conclusions.
Racism. It's racism and xenophobia.