Tobirama believes in rules and rationality. He doesn't hate the Uchiha out of prejudice, he just thinks they're a danger to the village. He worked with the Uchiha and intended to gave them a highly respected role in his reign.
Now that didn't work, but there the responsabilites lie on Fugaku and the others, not on Madara neither on Tobirama. People have to be held accountable for their own actions, not for what came after or before...
otherwise:
- Fugaku and the others aren't responsible for plainning the coup d'etat because the Uchiha were discriminated;
- the villagers weren't responsible for discriminating them because of the suspicion following the Nine-Tails incident;
- Tobi wasn't responsible for the Nine-Tails incident because he was following Madara's plan;
- Madara isn't responsible for his own plan because he reacted to Tobirama's ill-will.
- Tobirama isnt' responsible for his distrust because there had been a long time feud between Uchiha and Senju;
- Uchiha and Senju aren't directly responsible because it all started with the two sons of the Sage of the Six Paths...
And it goes on forever. This way of thinking is useless.
Tobirama didn't plan to exterminate the Uchiha. He may have made some questionable political decisions but that's all he's responsible of.