There is still a line between criticizing someone for being an asshole and dehumanizing them.
From reading the article it seems pretty clear to me that this guy is not a "maggot" but an idiot and someone who puts his own well-being over some principles that might be somewhere in the back of his head. So yeah, maybe a stupid asshole but probably not much more than many other people in any given society.
I'm not sure you are arguing in good faith because you seem to construct some strawmen there, like claiming I was only judging one side while I clearly called the draftee a "stupid asshole" and didn't even judge the original commenter's character but just said his wording was bad.
Anyhow, to the general point: I think it is almost always the wrong take to call out the little guys. Which country hasn't committed atrocities at some point? Is every US-American who didn't do everything to prevent the war in Afghanistan a maggot? Every Chinese who did not revolt because of Tiananmen? And yes, every German who did not die fighting Hitler? I think, no. The ones that did might be heroes, but I think those that did not are definitely not all "maggots" but just normal folks who didn't know what was going on, were afraid for themselves and their loved ones and so on. Which seems pretty human to me.
If you answer yes to the questions above, that is probably a defensible position, but I think the mindset that 95% of your fellow humans are potential maggots rather than just humans that have their weaknesses, like you and I probably do as well, is not very healthy. To me, it is mostly only the people in powerful positions who are pressuring 'their' people into committing atrocities who are the maggots. And yes, that would include Putin.
And lastly, to the concrete case: The guy did leave Russia and is not fighting anymore, so he might be a particularly bad example for you. I guess he mainly did it to save himself but from the article it does seem to me that his opposition to the war is at least a partial motivation as well. To use your line of argument: I think one should rather focus criticism on the political apparatus and the men on the front who are ardent supporters of the war rather than this guy.