"You're wrong, I'm right." Which political party has this mentality?

Republicans and Democrats are different ends of the same statist turd.  Those who subscribe to the twisted ideals of both parties wish to use the government to impose said views on others.  Only to adherents of the various flavors of state slavery is there some sort of illusory 'difference' between the two.  To anyone who gives even the faintest of damns about human rights and liberty, they're one and the same.  Both are wrong.

both

Both of them.

Both of the big two political parties have members who employ this approach...

Both of them

"All of them!"