Blake Shelton -- I Don't Have to See 'American Sniper' to Blast Celebs Attacking It

Blake Shelton has no problem defending "American Sniper" and ripping celebs who trash it, even though he hasn't even seen the movie!

Shelton was leaving 30 Rock (probably after his "Saturday Night Live" rehearsal) when he told us ... he was defending the military, not the movie itself, when he tweeted, "Sickens me to see celebrities or anybody slam the very people who protect their right to talk sh*t.. #truecowards"

Shelton admitted this week he might have been drunk tweeting ... but tells us he does plan to see the movie soon.

Kid Rock also went on the attack against Seth Rogen and Michael Moore, for their 'Sniper' criticisms -- writing on his website, "F*** you Michael Moore, you’re a piece of s*** and your uncle would be ashamed of you. Seth Rogen, your uncle probably molested you. I hope both of you catch a fist to the face soon."

Unclear if Kid was drinking, but chances are ...