Cleaning Copper Pennies

Cleaning things is sometimes complicated. For example cleaning used ammo cartridges is sort of a necessity. Cleaning a car gets dirt, salt, road tars off which could damage the paint and undercaridge. Cleaning a Mummy from an Egypian tomb could really do some damage. Cleaning your windows where you live allows more sunlight to get in and better to spy on your neighbors. Cleaning yourself helps in sanitation. HOWEVER, cleaning a coin usually takes of material and helps ruin it for collecting purposes.
Cleaning STUFF is sort of complicated.

I don't think anyone is telling you how to control your collection. I think they are just trying to look out for the benefit of the coin, and the value of your collection. It's a matter some people get very passionate about.

I tend to agree with you though. I have many coins that I have bought and or found, that for my personal collection, have cleaned. A cleaned 1877 Indian Head cent is worth more than an unrecognizable disk. If it's something I plan to get rid of, I leave it as is.