Right. It's valid to say that you will only use glass or polypropylene tanks because you don't like the idea of vaping from a tank that could leech into certain mixes of e-juice. It's also valid to say that you want to avoid cinnamon flavors because there's data to show that inhaling them is dangerous.
But the argument that we shouldn't vape something that "melts [polycarbonate] plastic" is a fallacious oversimplification. People eat cinnamon all the time, after all. The fact that certain flavorings have a destructive interaction with polycarbonate doesn't prove anything in particular about the safety of those flavorings OR the safety of polycarbonate in isolation.