It is not a very good or convincing reason......shinobis are often guided by hatred, they often define their nindo by hatred, revenge.....which may have nothing to do with any other matter.....if an uchiha is filled with hatred, does that mean he wouod mindlessly start attacking the innocent people of the village?? He may lose someone he loved, that is his personal loss, he will be traumatised, gain new powers and avenge that person's death but that doesn't mean he will kill people who had nothing to do with it...so why did tobirama restrict the uchihas for the sake of the village?