Ok Derek donates a lot of money to charity which is commendable, it doesn't make him a saint though. A certain Yorkshireman raised millions for charity but wasn't exactly a nice bloke was he? And no I'm not comparing Derek to him but you get the gist right? Lots of rich people donate (as do poor folk), it doesn't make them a perfect human being.
As for the Twitter comment, yes it was stupid, but it was completely unintentional so you move on. He'll no doubt post something far more offensive/intentional at some point which we can laugh/cringe at because that's his personality. He's brash and a bit of a balloon, he just happens to be bankrolling his local club and, for the time being at least, it's bringing on field results (which Leigh are rightly getting plaudits for).