I can see your point, but the nuances are all wrong IMO.
If you decide you can't wholly trust either side's testimony, you fall back on admissions.
In this case Suarez saying he said "Negro" once. - 4 match ban, and don't say it again.
The T-shirts thing - well, if you had said "Negro" and not intended active offence (i.e., you didn;t intend to be racist), and you were accused of saying "******" more than 10 times, wouldn't you like the support of your workmates?
The entire thing got out of control from the off with the suggestion of "******", thereafter, LFC had to back their man against that kind of accusation.
Remember all the to-ing and fro-ing about exactly what word had been used? No-one knowing exactly, until the FA deigned to come down from their high tower and tell us in the findings. It served their purpose to have this run and run so as to hand down a heavy penalty to put one over on FIFA and Blatter.
It should have been a much simpler said "Negro" 4 match ban, end of story, not a three ring bloody circus...