Yes, Marine boot camp uses a lot of mind games and pressure. Best to avoid it if you are ill.
Once you are out in the fleet the Corps also looks for reasons to pick on people. Not just the peer groups, but some senior NCOs and officers in the Corps also enjoy hurting people for being different, or making a mistake.
Th older I get the more I think America would be better served with a unified military service. Not just to even out things like the privileged life of an airman compared to the lot of a Marine, but to weed out the leadership traits raised in places like the Corps or the XVIII Airborne.
I think some versions of Traveller have addressed this, with even a new navy spacer getting a two man room, and E7 Marines or soldiers being in barracks rooms, among the other examples.
I don't think you have much direct experience with the USMC, if that is your understanding. Or you were in a bad unit with bad leadership, as that kind of behavior was simply not tolerated in any Marine unit I served with*.
While serving in 6 different units in 4 different commands after I left boot, I never saw or experienced what you describe... except for one person. He had been rejected when he applied to be a drill instructor - the reason listed was "tendency to over-punish instead of correct".
He tried to do the same to his juniors in our squadron, and was soon re-assigned to where he was under the constant supervision of a Staff Sergeant who didn't let him get away with his crap.
My squadron was assigned aboard a USN carrier (CV-61 Ranger) for 2 years, and I have personal friendship with several USN/USAF/US Army veterans who served at the same time as me and afterwards, and their descriptions of the leadership (or often the lack thereof) they experienced, and what I saw directly of the USN both aboard ship and in the technical schools I attended after boot, has confirmed in my mind that the leadership traits nurtured in the USMC are better for the men than those of the other services.
* If you mean there is a certain degree of informal testing and provocation that goes on when someone is assigned to a unit, then yes... we did test newcomers to see if they had self-control and an ability to "roll with the punches" and "give as good as they get" in an emotional/psychological way - physical hazing was NOT tolerated, nor was actual emotional/mental cruelty.
If the individual showed strength, we accepted them and the testing stopped. If they showed weakness the testing stopped then also... but we did not really trust them in any stressful situation. You see, combat is the last place you want to learn that someone can't handle stress and pressure... it is best if that is determined beforehand.
Boot camp is fine as far as it goes, but the people who are in someone's unit have to have personal confidence in that individual's mental/emotional strength, and that is best developed directly. A person can function effectively ans well in one unit, and completely fall apart in another just due to differing interactions with different individuals.