Romance's 'dumbifying' influence?

It's just a random line in a rather chaotic story about chaotic middle school years, but yet it is so particularly offensive.

The principal, Buffie Simmons-Peart, confiscates explicit romance novels with airbrushed covers, saying they have a “dumbifying” influence.

There's no further elaboration. Just that insult so casually thrown out there.

I was reading romance novels in middle school. Thick, adult, historical romance novels. I loved them. They keep me reading. I learned all sorts of history. They spurred on my imagination, my love of travel, my compassion for other human beings and empathy for their situations. My curiosity about things. All things.

What's so "dumbifying" about that?