That routine has absolutely fuck all to do with Hillborough, and the fact that you are so certain it does says far more about you and your anti-liberal-middle-class-metropolitan-sandal-wearing-humus-eating-cunt prejudice than about Stewart Lee or anything else.
It plays on the long standing comic stereotype of scousers as whiney, insular and complaining, which has been around for at least forty years that I can remember and probably longer (ie long before Hillsborough). I got the impression he was using that stereotype to send it up, though maybe not.
And whether it was an effective critique on UKIP is open to question, probably not as you and others seem to be taking the position that when a stuck up too clever for his own good comedian makes a joke about UKIP you don't like, it makes you more sympathetic to them and more likely to support them. This is not a coherent political response, but unfortunately this seems to be a significant source of support for UKIP, the knee jerk populist hate response, including from people like you who, with your professed proper political understanding, should know better.