Tell them about the dangers of an outdoor cat
Not only that but they could get worms and tics and all sorts of diseases
They could get hit by a car or stolen from you
And give him a litter box so you dont smell his craps
of course we have a litter box you can still smell it with the litter box especially since my cat is stupid and HAS to shit on the very edge of the litter box and dig the world's biggest hole to shit in. He has a half for if he's gonna shit and another half for if he doesn't shit. He's a fucking idiot and he has two litterboxes so idk why he chose the half half thing when he could do one for one and one for the other. My cat is fucking stupid.
And yeah I'll try but honestly it'll be hard to convince them, maybe if I talk about it love enough they'll be convinced.