That's not always true. Yes, there is a perceived "left-wing" bias, but truth be told, some of those concepts you've stated to be the gospel truth aren't always the case. For example:
On the 2003 version of Teenage Mutant Ninja Turtles, there were numerous minority villains. The Shredder (both of them) is Asian and Baxter Stockman is a Black mad scientist who was a major villain for numerous episodes. There weren't many heroes nor major allies of color on that show. Come to think of it, there weren't any on the 1987 version either. Bebop was a Black thug before he was transformed into a warthog, and The Shredder was still Asian, and voiced by a Black man at that. The Nahasaphones on King of the Hill are mostly antagonistic towards Hank and the others.
So, that explains why Penelope Pitstop won every race on Wacky Races. Oh, wait, she didn't. There aren't many female leaders of superhero teams, but there are female villains. There were also many instances on Justice League Unlimited when heroines got beat by their male opponents. They're not always victorious, you know.
The number one movie in America features a rich hero who's a weapons dealer unashamed of and uncorrupted by his wealth. The various Iron Man animated incarnations also showcased that side of him. Tony Stark's not giving money to charities and such. He's buying mansions and fast cars. Never seen any cartoons that celebrates being poor.
Multiculturalism is left-wing while bigotry, xenophobia, and hatred is right-wing? Is that even an accurate statement? What exactly is wrong with being exposed to other cultures? Or better yet, what's so right about hating people different than you?
Hank Hill on King of the Hill is one of the most noble characters ever placed on television. He's a conservative Republican who believes in traditional Christian values through and through. He's one of the last good guys on television. He's not a caricature nor a parody of one, and Hank's usually the only character that makes sense on the series.
Dale Gribble may not be the sanest character on King of the Hill, but he does respect and honor his right to carry arms and does so. He exaggerates a lot, and shows a bit of paranoia about the government, but he respects the 2nd Amendment.
Just saying . . .