If the EU behaves in that way, given its current state, it will break apart all the more quickly: you need an army to be able to bully your client states into submission.
If two parties agree on any contract or trade agreement, the parties are not always of equal weight and do have their own interests at heart. The UK needs the EU more than the other way around, so the EU has more pull and will make use of it. So "bully your client states into submission" is not a fair description to use, to put it politely. You could say that about any deal where one party has an advantage.
By the logic of your parent posters the UK wouldn't have left because of Greece, which has been used to set an example last year.