Former President Donald Trump’s presidential immunity argument against special counsel Jack Smith’s prosecution for January 6 is not just meritless, argued former federal prosecutor Renato Mariotti on MSNBC Tuesday — it’s also dangerous. By the logic Trump has laid out, Mariotti told anchor Ari Melber, if Trump was elected to a second term, he could order the military to lock up Joe Biden, and then fabricate a way to excuse himself from any criminal investigation of his actions. “When it comes to post-presidential immunity, it doesn’t exist, period,” said Melber, himself an attorney, as he rev…