Tobirama maybe a realist, but from we've seen throughout all of the Naruto manga, that isn't exactly a good thing. You could also say that he is the root of all the evil that has come from the Uchiha clan
He caused Hashirama and Madara to become enemies by spying on them. (though he was ordered to by his father)
He caused the death of Madara's brother, which in turn made Madara's hatred grow further.
His prejudice is what caused him to create the uchiha police force, making them think that he was showing them trust, when in fact he did so he could isolate them and keep a better eye on them. (Madara himself said the Uchiha's days would be numbered when Tobirama would become the 2nd hokage)
Hiruzen was said to be an idealist while Danzo was a realist. Hiruzen followed hashirama's teachings while Danzo followed Tobirama's. If we look at it from that point of view, we see Danzo has caused a few problems himself.
He was partially responsible for Nagato turning evil.
He was the main reason why Kabuto joined orochimaru.
He attempted to stop Naruto from saving the village by killing that summoned toad.
The moral of the story is, realists throughout the whole story have caused nothing but trouble.
They wanted what was best for their village. But the road to hell is paved with good intentions.
Idealists like Hashirama, Hiruzen, Jiraiya, Minato and Naruto have accomplished great things have all tried to create peace. (Madara himself was once an idealist until his clan and hatred got in the way)