I'm on the HOA board in my neighborhood and I generally think HOAs are okay within limits and when narrowly constructed. With that being said, $750 for that violation is ridiculous.
Politely ask the board to waive the fee. If they fail to do so. Never mention it again and never pay the fine. As others have said the homeowner is ultimately responsible. They can't do squat to you.
Friendly warning to all the HOA haters out there: Never pay your HOA with a personal check. We make a copy of your check in case we ever have to raid your bank account as part of a judgment.