you should talk —(also: you can talk) you are in no position to criticize because you are at least as guilty as the person you are criticizing (used as an ironic or sarcastic response to a person who has just spoken):
- “You are cold-hearted.” “You should talk of all people!”
you shouldn’t talk —(also: you can’t talk) = you should talk:
- “Andy’s always late. He won’t be here in time for dinner.” “You shouldn’t talk. You haven’t been on time for dinner for years.”