1. If you follow the manual and DRAIN your Atwood at least once a year,(better 3 or 4 times), you will not have a corrosion problem
2. Even HOME water Heaters require draining once a year and they do have anode rods.
3. I would like to see how a NYLON thread could damage the Metal threads in a tank---- ridiculous to state this. I Have never seen it in 40 years. You can cross thread the Nylon, but that just ruins the Nylon plug
4. ALL this talk and the simple thing is to just use the Nylon plug in Atwood. Is it really that hard and such a big deal? Just be proactive and drain your Water Heaters(Suburban and Atwood) on a regular basis. Takes 5 minutes.
5. ALWAYS drain either brand water heater when you are not going to use the RV for awhile. The water goes BAD in both brands and can smell awful