I'm going to be just a little pedantic, only to get my point across, not a fully formed idea here, just a thought.
The idea of a cancerous meme is certainly provocative, but its too big of a stretch I think and sort of tries to bridge an abstract concept and morality, as in the "war on terror" and the "war on drugs".
I say this because I do get your point, at least I think I do, but thinking of certain ideas as inherently harmful is the kind of thinking that gets you book banning in the first place.
If we were to follow the "cancer" analogy to its logical conclusion, we would then have to remember that cancer cells are normal cells that grow unchecked, (I am not a doctor, I know its not a perfect explanation, work with me here), so what are the checks for ideas?
Discourse, critical reasoning and the testing of those ideas to see if they're true, without which any idea can become dangerous, even so called good ones.
I would argue that banning this book actually qualifies as screaming for a cure to meme cancer, but as I've tried to make the point. Ideas are devoid of moral obligations like being good or bad.
Anybody arguing for or against the morality of an idea is really trying to avoid justifying a position under current circumstances by pleading to a higher power, in this case, morality. Now you don't have to prove anything, you have shifted the burden of proof to somebody else.