That's because many older people remember being sick with diseases that have since become preventable thanks to vaccines. I remember the long lines at a local high school for the polio vaccine. Parents couldn't vaccinate their kids fast enough. I missed a week of Little League baseball because my parents decided that at age 12, I was too old for the measles vaccine. I'll be getting vaccinated in a back alley if I have to, there's no way I'm going back to the 1950s.
Public opinion means nothing. Not to him, in his mind he's the best president ever. Not to his policies, which, despite mostly being illegal and/or unconstitutional, continue unabated. Not to SCOTUS, an unelected judicial body which answers to no one. Not to Congress, GOP-controlled and willing to let him do what he wants while they screw over Americans.
ICE will just round up some more brown people to make him feel better.