I put a lot on this earlier. He worked alongside and with people, who explicitly opposed busing as a means to uphold segregation. He openly admits to doing so, and says it was a worthwhile sacrifice.
At that time, that was the game in town. It wasnt an abstract discussion. The progressives in government were trying to break the racist states and their educational segregated systems, and that was the legal and practical method they had available to them. To oppose that method, working with who he did, ultimately upheld segregationist policies.
It is a little more complex, and there are caveats but it was a poor thing for him to do. However hopefully you can see now, that while he took the decisions he did, which ultimately did strengthen segregation, to me it would be too harsh to refer to him as a segregationist.
I'm not sure he believed in segregation. I think he believed in unity between democratic factions, and in the South many/most of them were either soft or hard segregationists. I suspect he disagreed with them, but was happy to accept aspects of the policy in order for unity.