That Joe Biden quote is not accurate, it is spread by rightwing social media to inaccurately portray what he said. He didn't say what that pulled out of context is suggesting
https://www.usatoday.com/story/news...e-biden-1977-racial-jungle-remark/6045749002/
No one is going to lionize LBJ, because of Vietnam. Don't you recall seeing old footage and history class courses featuring that famous anti-war slogan : "Hey hey LBJ, how many kids did you kill today"
Whether it is or isn't a slippery slope is a matter on what constitutes a slippery slope and if a slipper slope is even necessarily bad in all cases. If one is going to denounce the Confederacy and its support for slavery then I can't see how one can simultanously defend American imperialism against Native Americans.