When a person tries to make you believe that both sides are equally responsible for something even though one is really, clearly, at fault.
Trump's bothsidesism about the alt-right and alt-left is ridiculous.
From Paul Krugman's opinion piece in NYTimes, 8/18/17
Even before the media obsession with Hillary Clinton’s email server put The Worst President Ever™ in the White House, historians were comparing Donald Trump to Caligula, the cruel, depraved Roman emperor who delighted in humiliating others, especially members of the empire’s elite.
A noun for when a person tries to assert that both sides of a debate are equally X (reprehensible, reasonable, etc.)
Also "bothsideism" possible
A possible synonym of "equivocation"
Use of term accelerated with the Trump administration's refusal to denounce white supremacist and neo-Nazi groups, preferring to compare them to their protestors.
From NYTimes Opinion Newsletter, 8/17/17
"A forwarded email from President Trump’s personal lawyer defending the president’s bothsidesism on the violence in Charlottesville wrongly equates George Washington with Robert E. Lee, The Atlantic’s Yoni Appelbaum argues. “The analogy is central to the cult of Lee, to the mythos of the Lost Cause, and to the denial of what the Confederacy actually was,” he tweeted.