If you think it's just "showing respect to a piece of fabric", you'd be wrong. No one cares about the fabric of the flag, they care about what it represents. It represents our country, our personal liberties, and the men and women who die defending those liberties.
And if someone thinks they're being disrespected just because someone is protesting the country they're full of themselves. I mean how much of an egomaniac do you have to be to feel offended when someone protests a something that's wrong in this country. If anything people should be honored that more people are trying to fight to make the country a better place.
If you demand respect or gratitude for your volunteer work, you're doing volunteering wrong.