Ignore them. You'll get requests like this more often than you'd expect. Your opponent is just looking for a way to give themselves an advantage (or disadvantage you) so they can win. I've actually had them beg me to flee.
And if you don't do what they ask, they'll call you a "cheater". They may as well say you have cooties too. If you follow the rules that KI has established (and it's actually hard to break those rules unless you're purposely exploiting a bug of some kind), then you're playing the game fair and doing what you're suppose to.
I've had a few matches when my opponent has tried to convince me not to use certain spells.
I've had opponents tell me not to use Heal spells as "it's cheating".
One opponent tried to convince me that using Banshee was cheating. He couldn't explain why before I used my Banshee and snuffed him out.
Why do they think using certain cards is cheating? Surely, if I have them, I can use them.
I've only fought one PvP match so far. It was actually kind of fun. However, towards the end of the duel, my opponent said she was going AFK for a min., so, being a gentlemen, I held back and simply used defensive spells on myself... and then, without announcing she was back, I was attacked by a dragon spell of some kind. I went all out with the pips I had built up. One of her friends watching the duel told me that that wasn't fair, because she wasn't back yet... despite that she had just attacked me. As the rest said, ignore that kind of immature whining.
There is almost no such thing in wizard101 that is cheating. the only cheating card i have ever seen was chain stunning and they got rid of that . people tell you your cheating when they know there going to loose.
you know what i am a captain and i have had privates BEG me so flee and no healing and no judgement and all that and they report me when i heal or use cyclops so all you privates out there reading this stop cause nobody will do it.