They were not given the same punishment.
The other two, one of whom actually drink drove and seriously injured somebody, were fined 6 weeks wages and made to do community service.
Keogh was sacked.
At no point were Lawrence and Bennett forced to accept a new inferior contract or leave.
He got the chop because Derby's owner is scum.
I understand that, but I'm pretty sure all 3 were offered new contracts at a reduced salary as "punishment" (for lack of a better term). I believe the other 2 accepted that but Keogh didn't. Hence why he then got the chop, and it seems that the reasons behind that where for the same reasons you've listed above.
They all got the same treatment until he didn't accept the "punishment" so he got his contract ripped up. He obviously felt at the time that was unfair hence the appeal to Derby (which was rejected), then the appeal to the EFL (which was also rejected) and finally to where we are today via an employment tribunal.
I'm not arguing that it should or shouldn't have gotten to that stage, what I'm arguing is that he isn't blameless in the situation he has found himself in and that this will probably not get resolved anytime soon.