Stand up to him for what exactly? Marching into a Russian speaking enclave and fighting WITH the people trying to rejoin Russia, people who are cheering the columns of Russian armored vehicles as they pass by?
If he was invading Hungary or Poland it would be a different story.
However, and in complete opposition to my Chamberlain like stance, I find it impossible to forget that one of Herr Hitler's first moves was the unopposed annexation of Austria, something that was also cheered on by that nation's general populace. At the same time German forces began paying less concern to national boundaries and it has just been reported that Russian military aircraft now violate Finnish airspace with alarming regularity - something that is understandably alarming to the Finns who want no trouble with the Sovie.....err I mean Russians.
And now we hear that sanctions are bringing the Russian economy to near depression.
The parallels are not exact, but they are uncomfortably close to the events of 1935 - 38.