But science is not something inherent to a particular ethnic group that can't be used by anybody else. Magic is.
And even if we assume mages can be good citizens; groups and individuals pursue their own interests at the expense of others. It's an undeniable fact of life and mages are not immune to it.
With their special abilities, it would only be a matter of time until they dominated society again. Hence why restrictions are important.
I have to disagree with science. First, not everyone has the capacity to become a scientist. And even if everyone had access to it, it wouldn't make it less potentially dangerous. I am even tempted to say it would make it even more dangerous.
Power corrupts, yes, absolutely. Magical or not. But if human nature was truly that evil, I don't think society would have gone very far. Culture goes a long way in forming one's moral compass, and good education would probably assure that you would have enough decent mages to counter the ones falling to temptation, on top of the mundanes trained to counter magic the way templars do.
I do not disagree that some restrictions are necessary, I disagree with the way the Chantry and the Templars handled it.
The simple fact that the vast majority of mages in Circles were looking for a decent compromise before their hand was forced is proof enough that they were perfectly aware that with great power comes great responsability.