Keep in mind this was also incorporating the Paladin's code, as in UA Paladins were made a sub-class of Cavalier.
If our group banned Cavaliers, why would we ever play with Cavalier Paladins instead of PHB Paladins? Discarding the UA class also discards the part that says Paladins have different rules.
My guess is the writers naively expected the other party members to be treated as 'peers and equals' rather than 'beneath your station'. But, just like any other bit of 1e that try to overly restrict how one roleplays (e.g. hard-line alignment rules) it's best to just treat these as guidelines.
That's what I
would say, but the class description repeatedly goes out of it's way to emphasize how strict the code of conduct is and how the DM should adjudicate it. I think the book is very clear that the code of conduct is supposed to be rigid, inflexible, and deliberately onerous.
It's the UA Barbarian and their hatred of magic, magic items, and magic-users that's more in line with a class description that only has a
subtext of disruptive play. With Cavaliers, it's just text.
I've done it, and seen it done.
It needs a party run by Captain Kirk rather than Captain Picard, to be sure, as diplomacy with these guys is often pretty much off the table. But if you put the Cavvy in the lead such that his-her charge won't trample anyone else in the party, chances are you'll be OK.
Or, you could play characters that aren't so disruptive that they require the rest of the party to warp reality around your PC's obnoxious personality. There are, after all, multiple people at the table who want to play.
Yes, it's funny when B. A. Baracus has to be drugged with spiked milk every time the A-Team wants to fly, but that's because it's a throwaway gag every few episodes that takes all of 30 seconds. If you were playing in a game where characters routinely handwave away hours of air travel and now you can't because one player decides to play a character that refuses to cooperate, well, you've just forced everyone else at the table to stop playing the game and put up with your character trait whenever they want to get something done. It's hard not to label that obnoxious. It's hard not to say that you've taken your character and turned them into an obstacle. It's not really a huge leap to call a player-contrived obstacle disruptive to the game. It's certainly fine if everyone is on board with these kind of diversions, but if most of your table is expecting Henry V and someone keeps injecting Twelfth Night you shouldn't be surprised that you might upset some people.
That said, one of the best literary examples of a Cavalier I've ever seen is Mandorallen from Eddings' Belgariad series. Play a Cavalier as if it's him and you can't really go wrong. The trick is to have someone in the party that the Cavalier looks up to as a leader and whose orders s/he will follow; this gets around the 'cannot be controlled' bit.
I'm fairly certain that, on more than one occasion, the party has to distract Mandorallen and get him away from where the action is taking place so he doesn't immediately ruin the quest by attacking or killing some less savory individual because they
don't look the part. Mandorallen comes across as an idiot to be endured because his battle prowess was unmatched. Indeed, I'm fairly certain Polgara or Beldin said as much. Frankly, I find him a pale shadow of the Pandion and Cyrinic Knights from Eddings' other major work.
These kinds of character traits might make for comedic moments in literature, but like Kender and Gully Dwarves it very easily makes gameplay
excruciating. It means that one character gets to dominate every interaction with NPCs to the extent they their characters must be effectively
taken out of play before anyone else can play the game. It means one PC has to be "dealt with" before the rest of the party can actually roleplay their characters.