Sorry, but your' going to have to go a lot further back. Do you not recall the RW trying to pin murder on Bill and Hillary Clinton? If you really want to find a source for much of the toxicity in today's politics, look no further than Newt Gingrich.
We can keep going back and back. I guess the main reason we notice it more now is the internet and social media in general.
Yes Clinton was attacked, Bush I not so much, Reagan was attacked, Carter has been attacked moreso after his presidency. Ford was made fun of more afterward as well, Nixon is a special case, as he was almost impeached, and from what people say, not a very personable person. LBJ was the demon spawn according to the radical left... and we can go on.
Honestly I think the only president everyone liked in the past 60 years was Ike. JFK was close, but you had the whole "Papist" thing.