Yah, I came across a similar thread and thought of the same thing as you and now I hate Tobirama. That bitch is responsible for the demise of the relationship between Madara and Hashirama. I'll provide a few manga scans.
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As you can see in the scan above, Madara and Hashirama having a friendly chat until Tobirama interupts and you can see by the impression on his face that he means trouble. Madara then responds by thinking "wtf does this nigga want?"
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Then on the next page, Tobirama feeds Hashirama with info on what he believes to be the case as well as trying to hide it like he's giving some advice. While a suspicious Tobirama bring out the feud between Uchiha and Senju once again in front of Hashirama, Madara overhears and feels bad.
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On this page, Madara begins to show his concern for the Uchiha Clan after hearing Tobirama. He felt as if Tobirama would exterminate the Uchiha Clan if he were to become Hokage which was a possibility.
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Next page, Madara implies even more clearly now that Tobirama is the cause for all of this. Since he previously brought up the history of fighting and resentment, Madara felt insecure and showed his desire to protect the people he loved. He wanted to protect his brothers but failed, then he wanted to protect the Uchiha Clan who were next closest to em but they didn't listen. His love was betrayed a number of times so he began hating the World for how it was. He even started to lose his trust with Hashirama because of what Tobirama had said to em, maybe he'll listen to his real brother.....