Well, tatooine would, but where's all the water?
From a guy's perspective:
As a male exile his harshness towards others comes across more as unspoken loyalty.
Well Atton is only kind of creepy, playing as a fem exile. But so was it kind of creepy from disciple and you could see his moves a mile away. All in relative senses.
As either male or female exile, Atton won't admit it but there is a lot more care and loyalty under the surface. Plus to go from jedi killer to remorseful and even "atoning" about it says a lot as well.
As far as him being harsh
1)towards Handmaiden... Remember the saying "bros before hoes"? He's looking out for your male exile and it isn't exactly without good reason because if you'll recall she *was* first to confront you on Telos' polar academy AND she *did* sneak aboard. Suppose it's also a tad personal/professional, she works for the republic, he doesn't care too much for the republic.
2) As far as his treatment towards Disciple...well, it's a cultural and male competitive thing. Disciple is like a royal gentleman hopelessly doomed to be stepped on and "just friends" in a more American like society--poor chap. Granted, Atton is being like a typical American guy--a jerk. But it's not all jealousy, it's competition too. Perhaps mingled with dislike for the republic which disciple serves.
EDIT: Well, Mira did catch him eavesdropping, and outlined his flaws which *do* come standard on a regular guy.
Far as Carth... whiny in either case but openly and undeniably loyal--you have to be the one to betray him. He does eventually have a legit reason for his issues.
As a male character, I wouldn't exactly call him bro but I suppose like a good neighbor. Maybe like family given enough time and knowledge of him.
As a female character...Carth's approach isn't the way I'd go about hitting on fem revan if I were in his spot. However, the writer *did* at least get the confidence part down (if nothing else). Confidence works for any guy's game. Period.
He never does let you go wrong though his methods may lack firmness and resolve at times. His main concerns are the republic and isn't sure about the mandalorian. Canderous, bah, he's like an old biker dude and probably has women-squeezes everywhere; a bit of native American Warrior IMO (speaking as part Native American myself). Anyways, I always do at least try to have it so Carth deals the killing blow to Saul.