When you live in a home that is governed by an HOA, you know the rules before you ever move in. Respect them and abide by them. As one lawyer friend of mine who specializes in HOA law once told me: "If you don't make the homeowner take down his Penn State flag today, you've given up the legal authority to make his neighbor take down a Nazi flag next month."
Please be aware that the rules can be changed by the HOA governing board.