Yes, it most definitely is FUD, and he was spreading it, though not nearly as thickly as you.
Pure H2O is possibly the most corrosive chemical in the universe and IS certainly the most corrosive chemical in the known universe.
I think the phrase you're looking for is "universal solvent". Oxygen is the most corrosive chemical in the universe, AFAIK. Solvent != corrosive.
The second the stuff hits your mouth it'll leech all the minerals from your teeth.
Utter bullshit. The leaching process would be so slow that you'd have to leave a tooth in a glass of DI water for a long time before any substantial amount of minerals were leached out of it.
God only know what it would do to the soft tissues, but you can be certain the sodium will be gone and the cell membranes will collapse due to the saline imbalance.
Water passes through a cell membrane much more easily than those ions, so no. Osmatic pressure would cause the cells to fill with water until they burst, but regular tap water will do the same thing. It would not instantly suck all the ions out of your cells, by any stretch of the imagination.
It would literally be safer to drink lye.
Why don't you go and do that, moron. Meanwhile, I'll be drinking RO water, just about as pure as it can be made.
I remember in college a problem we had in the physics department, they were using super clean water because they needed to minimize diffraction through it, and within a couple hours the vessel holding the water shattered
Correlation != causation. I'm sure plenty of people have kept super-pure water in glass vessels without experiencing that problem, so the onus is on you to prove what you claimed next:
because the water had sucked all the minerals out of the glass.