Something the government seems to have forgotten: freedom of speech and expression includes the bad as well as the good. Freedom of speech doesn't mean "only the stuff we like". It doesn't mean "no criticism". And if someone feels that the government has done wrong and chooses to express it by burning an American flag in protest, then he should be allowed to do so. Besides, we're not talking about something that is a problem in this country: The Citizens Flag Alliance, an advocacy group that supports a constitutional amendment, reports a decline in flag desecration incidents, with only one this year. One. As in "not something to be amending the Constitution over".
Frankly, with all the crap going on in the last several years (blatant lies, false accusation, prisoner torture, civil liberties abuse, segregation of dissenting views, etc.), I don't think they have any room to talk about "desecrating the flag". They've done far more than any of us ever could towards making the US look bad.
(And, as a side note: is it just me, or do you feel that amending the Constitution is something that should be saved for only the most severe needs? Man, I just twitch every time I hear that the Government is trying to amend the Big C over something. It's supposed to be the document that helps spell out the way this country is to be for everyone, not something for petty political squabbles. Flag-burning? Gay marriage? These are not issues worthy of Constitutional inclusion.)