PSU Molex Removal

Anytime you leave cut electrical wires that aren't properly terminated and still connected at the source, you're risking some type of hazard. Your PSU would still work, but what you're suggesting is highly unrecommended and, quite frankly, dangerous 😛
 
You can cut them off, but you have to be careful to not let exposed wires touch anything - in that case, it may not just destroy your PSU, but your entire PC. But realistically, it's an awkward solution for a non problem, it's far more logical to use fold up unused cables and with some ties, hide them neatly somewhere.