If a thing has never happened, and I have NEVER, not once, heard of one corn being dominant over any other nor have I EVER heard of them fighting, what is the likely hood that it will occur?
It's possible that a meteor will knock you silly next time you step out of your house. Do you wear a hard hat every day?
It's all well and good to be cautious but you were passing judgement, saying absodamnlutely that a thing was not good and THEN you had the gall to throw in reasons that HAVE NO FACTUAL BASIS.
This is what I am driving at. YOU, as an experienced keeper are passing on to a newbie information that YOU, the experienced keeper have NO clue whether is true or not. You have assumed that it is because it suits YOUR point of view, when the plain and simple facts are you are incorrect.
Keep them apart or in groups of a thousand, makes no nevermind to me. Just don't pass down nonsense as law to those who don't know better.