He was regretful of it by 1944, at which point he stopped advocating against the internees being allowed to return home. Looking into it it does seem he was significantly worse than many others, but you're still overstating things as even without a public apology (which he should have made) he was regretful before the war endedMost apologised, Warren refused to. While broadly people may have supported it, Warren took an active part in it, more so arguably than even DeWitt. After internment, he still fought to keep them out of California. Even Stimson wasn’t that detestable, and he signed off on the damn executive order.