When SNL first started in 1975, they mocked former President Nixon and then President Ford relentlessly. Same with every President until Barack Hussein Obama, when he was deemed off-limits. A proverbial woketopia because the sainted One was too cool for school. Obviously we all know how the late night shows treated President Trump.
Everyone is fair game in politics, regardless of party/race/gender/lack-there-of. Johnny Carson/David Letterman/Jay Leno/Conan, et al used to ridicule everyone equally. Eventually Letterman got old and bitter and stopped being funny, just attacking conservatives. It seems that the other late night hosts simply followed suit and started singing from the Democrat party sheet music rather than entertaining audiences.