It's not demeaning, it's cute! But Tamaki can argue about his choice of nicknames later. At the moment, it's not clear if he even knows what honorifics like "chan" actually mean.

"Eh... I don't really get it." Tamaki shrugs and scratches at his head. "I possessed Lam-san to go to the cat cafe. And then I talked to the earth spirit and realized I'm not really dead. Now I can go anywhere."

Bullshit ghost mechanics.

Although after dispensing that explanation, something occurs to him. "You know about the severing?"