The argument makes a false equivalence between what the Democrats have been doing and what they are afraid Trump will do.
The Democrats have been targeting conservatives and Republicans and using novel excuses to charge them of a crime.
Meanwhile, the Democrats have been committing actual crimes of which there is no doubt, but use novel excuses why not to prosecute them.
If Trump’s Justice Dept prosecuted those Democrats, it would not be the same thing because those Democrats actually did break the law.