First of all, let me say that it's possible to get too focused on the most extreme reactions and say they are representative of the whole.
I know that this sentiment represents a small section of America, but especially if the Democrats win the House and there are hearings and talk of impeachment, expect this sentiment to become stronger.
Perhaps it's because I grew up in the Cold War 1960's, but if you were to show Barry Goldwater that T-Shirt he would think it was from a dystopian future. Who's the big winner in that T-Shirt? Vladimir Putin. 'The enemy of my enemy is my friend', as the saying goes. These gentlemen have forgotten who the enemy is. In George Orwell's 1984, a central tenet of The Party is the mutability of history. "He who controls the past controls the future. He who controls the present controls the past." Think of these T-Shirts with respect the history of the last 2 years. The first 'truth' was no collusion. Now that 'no collusion' is beginning to lose its luster, you're seeing a move towards 'collusion is not a crime', the justification being that it is perfectly normal to want to get political dirt on your enemies. 'No collusion' was yesterday's truth. We have always been at war with Eastasia, as well as the Democrats.