These people that 'don't get' South park are probably people that remember it when it first started out, when it was just toilet humour.
Now it is quite simply the best piece of TV there is. It is far cleverer than the others and very relevant as it focuses on topical issues and satire.
You also can't help but agree with nearly every message they put accross, every single religion has been a victim of their expose and it usually makes so much sense.
If you do start watching it make sure you catch it from series 5 onwards.