What are you guys whining about? If everyone uses the same deck just build a deck that works well against that specific deck > Win every time.
Or is it that your deck loses against these rainbow decks and instead of changing deck you want to force others to change?
Rock is OP, Paper is OK.
-Scissors
I'm also against this "guilt" system. Why would you make the AI not play what's most beneficial in that situation. His mission is to mercilessly crush the opponent, not to figure out the least frustrating way to do so.
Let everyone play as they want, with the cards they feel most comfortable with.