Not to beat a dead horse, but...
Food for thought. Meguiar's has MSDS for all their products available online so I simply use them as an example. Proctor & Gamble (Dawn) also has their MSDS and ingredient lists available. Doing a side by side comparison of Meguiar's Deep Crystal Car Wax and Ultra Dawn Original, they BOTH use sodium lauryl sulfate as their primary surfactant/cleaning agent. Dawn also uses sodium laureth sulfate as a primary whereas Meguiar's uses Cocamido Propyl Betaine, a surfactant derived from coconut plants. The point is, it appears by and large that the main ingredients used for dish detergent and car detergent are the same. The difference is in the details. Dawn lists several more ingredients, among them sodium chloride and magnesium chloride, both salts. Meguiar's doesn't list all their ingredients in the MSDS. So when you argue about degreaser, understand that both car and dish soaps use the same one (at least based on the quick browse I did through Meguiar's MSDS sheets.) Furthermore, it only makes sense that Dawn recommends not using their product for anything other than its intended use. All companies do this, if, on the off chance that something unintentional and probably unlikely will happen, they can't face litigation. Just think of all the ridiculous warnings you see on chainsaws, toasters, blow torches, etc. Just use common sense when using these products. Yes, Dawn contains sodium chloride, and yes, it may corrode, but if you live where I do, your car is bombarded by salt to the magnitude of 50x the amount in Dawn every winter when the snow plows cover the roads in it.