I'm not a lawyer, but I believe those are the parts that pertains to this issue.
If a shop lifter steals £100 of goods from Sainsbury's, they are criminally liable for the theft, possibly resulting in prison. They might receive an extra punishment from the supermarket itself in the form of a ban. If they are an alcoholic, with a history of stealing wines and spirits, the court might even issue some kind of order forbidding them from entering off licenses and all supermarket wine sections.
None of this would breach their human rights as the punishment would be proportionate to the crime, and no agency would be exceeding its powers.
If a benefits cheat steals £10,000, they are criminally liable for the theft, possibly resulting in prison.
The DWP though cannot ban him from its services. If Sainsbury's ban the alco shoplifter, they are not making it impossible for him to buy food, he has other shops to hand for that. If the DWP refuses to serve the man, they are saying: in the future this man has a choice between being a smelly tramp, or being a thief again. If we're going to do that, then we may as well ban him from the NHS as well; in case of heat attack, do not resuscitate, he doesn't deserve it.
The trial judge wouldn't be able to enforce such a punishment in the first place as it breaches UK law, being quite clearly cruel and unusual. So it is only if the DWP applied the punishment under its own authority that a European court would ever see the matter.