I mean, sure, Reunion has too many of those typical anime-style "mwhahaha I'm such evil look at the edgy rubbish I say HA HA HA" characters so you can't really sympathize with them. But their motivation in principle makes sense to me. And wishy-washy Rhodos with, sure, an admirable goal of "we want everyone to get along!" but a rather nebulous plan on how to achieve it is ... weird to me.
I feel like only Mephisto is the outright FOR THE EVULZ Reunion member.
P much. So far their other commanders (aside from Faust, whom he's close with apparently thanks to shared history) we've seen interact with him have done so with open disgust and revulsion - or as icicle bunnyFrostnova greeted him, "I should have left you freeze to death like the psychopath you are."
The others, whatever you now think of their methods, seem to be various flavors of Well Intentioned Extremist (Patriot judging by his event convo with Hellagur, Frostnova) and/or out to avenge legitimate enough grudges (original Skullshatterer), or plain old Punch Clock Villain hired help (W and the other Sarkaz mercs). Crownslayer and Talulah are so far anyone's guess.
As far as the setting goes do keep in mind that as far as can be discerned from the assorted Operator bios etc. Ursus treatment of the Infected is from the harsest end of the scale (likely an unsubtle allusion to Imperial Russia's track record with antisemitic pogroms) - and Chernobog is suggested to have been vicious even by their standards, which is probably why it was Reunion's first target once they moved to open armed revolt. Other societies are implied to be more tolerant though the Infected are still very much pariahs - which is actually understandable if you think about it and keep in mind this world has had to live with it presumably since before the dawn of history; the disease is effectively untreatable (even RI's cutting-edge medicine can only halt its progress and alleviate symptoms), inevitably lethal untreated (see previous), the victims' corpses become virulent infection nodes themselves, and as icing on the cake side effects can include diverse dramatic, ghastly and/or dangerous physical and mental changes.
Against that background it's not really surprising even the most tolerant communities are inclined to exclude the Infected from polite society (Op bios suggest many duly make their living in or outside the margins of law); it's an only too obvious social mechanism for both isolating an inherently dangerous element and creating emotional distance to what are for all practical intents and purposes dead people walking. Which of course doesn't stop families with the means to do so from doing what they can for afflicted relatives (this being how several Ops ended up at RI in the first place) for example, and Oripathy seems to be something of an accepted occupational hazard in certain fields - including Disaster Messengers, a for fairly obvious reasons highly-respected job. It can be assumed the disease carries considerably less social and cultural stigma when associated with such inherently hazardous occupations - Blacksteel referring Franka to RI for treatment after her infection is probably a good example.
Returning to Reunion, the fundamental problem with what they are doing is twofold. First, it's basically only a matter of time until their rather aimless uprising gets crushed by the organised states of the world - IIRC the Lungmen bigshots are already finding the lack of overt military response on part of Ursus both puzzling and highly suspicious - and the only real question is how much damage they manage to do before going down, including to Infected status in the wider world.
Which brings us to the second point which is probably the big reason Rhodes is so opposed to them (leaving aside whatever convoluted X-Files business may be involved in the whole mess and Kal is keeping locked up in her desk drawers) - it automatically polarises and aggravates Infected-Uninfected tensions everywhere. States that so far have to varying degrees tolerated the Infected in their margins now have to start viewing them as potential fifth columns for revolutionary violence which can only result in unpleasantness and major uptick in mutual distrust. (Which is ofc one of the oldest tricks in the extremist playbook; remove the middle ground so "their" people have to flock to their banners for protection and lack of alternatives.) This is immediately evident ingame in the Lungmen segments and also comes up in some Op bios - a riot by Reunion supporters was the proximate cause for the rather bizarre reason Skyfire and the rest of the King's Wand research society signed up with Rhodes to fight the movement, for one standout example. On the other side of the coin Ethan used to be a Reunion activist; he presumably bailed once the movement started getting alarmingly militant.
...probably best keep him well away from Zima and the other Chernobog survivors, just to be safe. >_>