There was a certain ambiguity to the situation. These people were Germans, not Czechs. And Hitler asserted that this was his last irridentist claim. Given this ambiguity, it made it easier for some to appease Hitler rather than confront him.
Vladimir Putin's claims that "Russian speakers" are being mistreated are ridiculous. Nearly everyone in the Ukraine not only speaks Russian, but uses it as the main language in their daily lives. Da...even in Kiev.