Toxicity is always a function of concentration. Always. Even water is toxic if ingested at high enough levels.
This (the water part) is one of those things that sounds clever at first and then obviously isn't when you think about it some more.
Sealed plastic containers are highly effective at controlling bacterial growth, for example.
We could and do use other kinds of containers with a plastic seal which is not in contact with the contents during storage.
Flossing your teeth with plastic (nylon) is universally recommended by dentists for dental health. [...] Many of these health-*positive* uses would be very difficult to reproduce with other materials.
Nylon is notable in large part because of its stability. This means it leaches less than do some other plastics. Not all plastics are created equal, and we shouldn't pretend they aren't. Nylon is one kind of thing, and Vinyls are another kind, for example.