The rock star hurled the insult and some other choice words at Trump after he pulled the United States out of the Paris Climate Agreement on Thursday.
"Dear Donald Trump. First I want to say f-ck you. F-ck you for pulling out of the Paris Agreement," Armstrong began the not-so-sweet letter to Trump he posted on Instagram, along with a photo of the Earth. "The future of planet is in more danger now than ever. Your lies and rhetoric are making the world toxic and unsafe. Now the human race is officially an endangered species."
"Second I want to say your days in office are numbered," he continued. "You will now officially go down as truly the worst president in the history of the united states. You are unqualified. You are a bigoted half wit asshole reality star that has made America a joke to the rest of the world."
Armstrong concluded the message with, "I hate your guts. And mark my words, we are going to take you down. you're fired. sincerely f-ck you," signed, Planet Earth.
Armstrong is just one of many voicing outrage over Trump's decision to pull out of humanity's biggest climate agreement in history.