This would be a better argument if it wasn't shown in Oblivion that they can coexist with the general populace just fine if given the chance. Sure, some Khajiit are thieves, but the game is mainly drawing on Gypsy stereotypes and actually has the same justification for them.

Not giving the Khajiit the chance to prove themselves trustworthy, ostracizing them from society and ensuring they HAVE no legitimate and legal means of employment ironically instead incentivizes them to say "Fuck it, praise Baan Dar!" and live up to the exact stereotypes you put on them.

It's a never ending self-fulfilling prophecy.

Khajits: "Everyone is out to get us because they think we're untrustworthy thieves!"

Also Khajits: "We start with positive modifiers in Sneak, Lockpicking, and Pickpocketing, out culture abhors the concept of law and exalts the virtues of trickery, and our caravans are the best reliable source of narcotics in all of Skyrim."