Why?  Because they know that Browder's story about Sergei Magnitsky is a lie.  And that means that when you tie in the Trump Dossier, Christopher Steele, Fusion GPS, the Skripal poisoning and the rest of this mess, these men are consorting with foreign governments and agencies against the sitting President.

As Lee Stranahan pointed out recently on Fault Lines, Cardin invited Browder to testify to Congress in 2017 to push through last year's sanctions bill, a more stringent version of the expiring Magnitsky Act of 2011, which has since been used to ratchet up pressure on Russia.