By Zoe Delaney Oscars host Jimmy Kimmel’s joke about Robert Downey Jr’s past drug use during his opening speech didn’t go down too well with the Ironman star – or viewers watching at home. Jimmy took to the Oscars stage inside the Dolby theatre earlier this evening to host the 96th Academy Awards, delivering a classic opening monologue full of jokes. The comedian targeted several celebrity guests after warning earlier in the week that nothing was “off limits”. The 56-year-old proved this when he made a joke about Oppenheimer star Robert Downey Jr and his past struggles with substance abuse wit…