Considering I've met some pacifists with that exact stance, then yes, yes you would. That wouldn't make you right, or correct in any way, but it would make sense. And a lot more sense then going "well the soldiers don't think they are doing wrong, so I don't have the right to judge them."
Most people would be okay with things in context. Like a cop killing someone attacking others. They don't approve of murder, but they'll make an exception for a trained professional protecting others. And I'd say I'm okay with mind control in a similar context. Like Dabbler controlling Jabby when she was attacking people. Or if, hypothetically, Peggy lost control and pulled a gun and tried to shoot Parfait. Key part being that lost control stuff. No preempting anything because by that same logic everyone could/should be mind controlled all the time so they don't commit any crimes.
Dabbler can argue what she's doing is for the benefit of the team, but she doesn't have the right to make that call. Particularly when it comes to the second part, protecting her sister from the consequences of her action. Particularly again, when the people in question are right to be angry.
Basically Sydney and Parfait messed up big, and normally people would be upset at them. To the point of holding grudges about it apparently and maybe even causing members of the team to be kicked out or quit. Same with Sydney for that matter. Would Sydney have forgiven Parfait's sexual assault if her ability to be upset wasn't being suppressed? They messed up, they should face the consequences of the emotions they hurt so they can properly make amends for their actions instead of them thinking everything is hunky-dory.
What's more Dabbler knows that Maxima (her commanding officer and person in charge), would flat out forbid Dabbler from doing anything like this if she knew about it. For that matter, most of the team would likely say the same thing (apparently Gwen is okay with it). So she's going behind everyone's back to mind control them. Rather than, you know, things getting out of hand and then Dabbler suppressing emotions and telling them about it.
Finally, and this is the kicker that puts Dabbler into the 'monster' category for me, she sees nothing wrong with any of her or Parfait's actions. This isn't 'a regretful necessity for the greater good' or even 'I'll do anything to protect my baby sister', it's 'this was a good thing, and I'll prevent anyone from thinking otherwise.' Both Dabbler and Parfait seem incapable of thinking that what they did was wrong. Like you know, a monster who is incapable of understanding why eating people would be wrong.
Or to put it another way, you said Dabbler and Parfait know they've done wrong. This page disproves that notion as Dabbler's attitude is that they are 'rescuing' archon from not having sex. That Parfait's actions were an achievement to be lauded, not be upset at. And that emotional suppression to prevent anyone from being upset is a perfectly reasonable action to take in response. If Dabbler thought she was doing something wrong, then she'd treat this with more gravity.
Even Parfait seems more upset at the idea of embarrassing Sydney and Dabbler than at the idea of 'hey I might've just ruined someone's relationship' part of things.