> Don't pretend like the Democrats wouldn't be just as obstructionist if it suited their political objectives.
So if someone throws a stone at you, you might reasonably be tempted to throw a stone back. If called up on this, you might be tempted to say "he started it". Legally speaking, that might or might not be a defense.
What if instead you throw a stone at someone and justify it with "he was going to throw a stone at me"? Would you consider that a sound defense?
Take it further. Your defense becomes "he would've thrown a stone at me if he had the option so I had to throw the stone at him". No reasonable person would respect that argument.
So why is the hypothetical "Democrats would block a Supreme Court nomination if they had the chance" reasonable to you?