I think the exact opposite is true: they use the excuse of pragmatism while arguing exactly in favor of what they idolize. It'd be more convincing if their concessions to anti-socialism advanced or preserved leftist causes, but largely that's simply not the case. What you described is the exact problem some Anarchists have, where they idolize praxis to such a degree that they argue against making optimal moves in favor of keeping themselves ideologically pure. Anarchists sometimes argue against voting on principle whereas Tankies will argue that you should vote for the newest ML party. The ML party will decry not doing enough for workers, propose nothing of substance, and call Biden evil for helping Ukraine resist Russia.