Idiot
Dumb, Fool, Stupid, Absurd
noun, な adjective
A horse deer is a stupid idea. You're an idiot for thinking about it, really. It's quite dumb.
You learned both of these readings when you learned the kanji. You should be able to read this on your own.
お前がそこまで馬鹿じゃなければ、お前がどれだけ馬鹿なのか説明することができるんだけどなあ。
If you weren’t so stupid, I could explain to you how stupid you are!