"Treason" is an extremely strong word, and not one people should throw around so freely. There's a reson it's the only crime defined in the US Constitution; the country's founders knew that governments tended to use "treason" to mean "dissent against whoever is in charge right now."
Dissent, even very strongly-worded dissent, is not treason. Treason is "levying war against [the United States], or in adhering to [the country's] enemies, giving them aid and comfort." I suppose some people think that criticizing the government or its agents (including our military) is "giving aid and comfort," but that's taking things too far.
Anyone who throws around the word "treason" against opponents of the current government should be really careful, unless of course you assume that your friends will be the Permanent Government. Assuming the opposition comes into power again someday, those same charges you levied can be turned against you.
But of course, the tendency of whoever is in charge to try and silence the opposition is an old tradition. For the USA, start with the Alien & Sedition Acts and move onward from there. I simply hope we will eventually retreat from the current swing, just as we always have before.