There is nothing to prove. It is a fact. Grass grows, birds fly, and tap water corrodes metals. You even said yourself that you clean crap out of your setup periodically. What do you think that crap is? Calcium, lime, chlorine salts, zinc, and perhaps even actual salt! If your arrogance ever subsides and you decide to use a proper cooling solution perhaps you wont have to clean that crud out of your system all the time.

Just so we are clear. Your recommendation is that it is safe for everyone to use water out of their tap for their cooling loops?