Why can Obama attack Trump with impunity but every Trump tweet that attacks his political opponents is branded as horrible

If they didn't have double standards Democrat politicians and the #FakeNews media would have no standards.

Joe Biden clearly displays signs of declining mental capability and Democrats and the #FakeNews media ignore it. But those same leftists say that because Trump disagrees with them he's mentally unfit to be President.

Now Barack Obama viciously attacks Trump and the leftists cheer.  If Bush had done that to Obama we all know the leftists would have screamed bloody murder.

But more importantly every time Trump attacks his political opponents in a tweet leftists condemn him.

Clearly there are two standards, one for Democrats and one for everyone else.