If Russia is willing to continue the war as long as they're making gains (and Russia is making gains as long as they control foreign territory and intend to keep it), refusing to military support Ukraine means supporting a scenario where Russia will have effectively violated their sovereignity, which in turn further incentivizes imperialist countries to attack their neighbours as they've just seen they can get away with it.

You can keep gaslighting yourself into thinking that you only need words to convince Putin to leave Ukraine, or for Netanyahu to leave Palestine, or for Jeff Bezos to give up his privileged position in the capitalist hierarchy, but the vast majority of the world will keep their feet in reality and understand that some people are fundamentally selfish and must be forced into no longer committing evil.