It's hardly infantalizing or diminishing to Lucy's and Maximus' characters.
Max wouldn't "judge" Lucy for being violent, because he understands that sometimes it's neccesary. Sometimes that's how you survive in the wasteland. He's done so himself to protect his life and even urged Lucy to do the same when they encountered the fiends (and then resorted to violence himself once she wasn't capable). He wouldn't judge her for it.
The times we've seen Maximus go through with killing people were self-defense of himself or another party (which was the case with the fiends and Xander). He also technically killed Titus by refusing to lend him aid, but Titus was also being a big jerk to him. And while he planned to assassinate Quintus to try and stop the Brotherhood civil war, he couldn't go through with it because the process of planning and deliberately confronting someone with the intention of killing them is different from spur-of-the-moment occasions like the other ones.
And I think when I refer to Maximus potentially judging Lucy...
...well, honestly, I don't think Lucy nor Maximus know each other all that well. They didn't spend that much time together in season 1. Seriously, only maybe three to five days tops pass between when she meets up with him in episode 5 of season 1 and when they part ways at the radio station in episode 7, plus their brief interaction in Filly in episode 2, and their brief exchange at the observatory in episode 8 that was cut short when he got knocked out by her dad and she had to abandon him to depart with the Ghoul because she'd be killed by the Brotherhood reinforcements when they showed up.
Given how little time they spent together, well, honestly they're still complete strangers to one another.
The way Maximus talks about Lucy with Dane and Thaddeus, he comes off to me like he's got some idealized image of her in his head. And since they parted ways, Lucy has shown that her morals have started slipping, and she's done things that wouldn't necessarily gel with this image Max has of her (like doing the whole The Good, The Bad & The Ugly "bounty" scam with the Ghoul, taking chems and rationalizing doing so, stealing things because she doesn't have enough caps, or being willing to chip her own father for selfish reasons).
On Lucy's end, well, we don't know what she thinks of Maximus. Seeing as in season 2, she never discussed him onscreen at any point with either the Ghoul or with her dad, and there's no hint that she had offscreen discussions about him with the Ghoul. And she and Maximus weren't reunited until the final scene of the season, at a point when she was also in a bad place mentally due to her father having just effectively killed himself. If anything, I could argue Lucy actually knows more about the Ghoul than she knows about Maximus, considering that she and the Ghoul traveled together all the way to Vegas over the course of several weeks. (I'm not saying that as a Ghoulcy shipper, I'm saying that as someone looking at things with a more analytical perspective.)
Now, since Lucy ended the season reunited with Maximus, season 3 will undoubtedly open with them in some kind of relationship while also dealing with the NCR-Legion conflict and Lucy trying to find out what her dad was up to and who was pulling the strings behind him. And they're probably going to be an endgame pairing (because for Lucy, she'll either end up with Max, with the Ghoul, or single).
For me, I hope that in the early episodes of season 3, the writers will address with Lucy and Maximus the fact that they've changed since the end of season 1 in what they want in life. Lucy's not the naive vault dweller she was when Maximus first met her, and Maximus is no longer part of the Brotherhood of Steel and is trying to forge a new identity for himself, one that's likely with the NCR (a faction Lucy might not necessarily hold in high regard, considering how the Ghoul's ways of thinking have rubbed off on her).
And they'll have to determine whether or not Lucy and Maximus are indeed a good match for one another. Are Lucy and Maximus a good match at this point in time? Or is this just a relationship of convenience that Lucy is in due to Maximus being the first person she met on the surface who was nice to her (and as of the end of season 2, because the Ghoul isn't around for her to travel with), and that Maximus is in because she's the first person he formed an emotional connection to that wasn't affiliated with the Brotherhood?