It was fairly clear, from the original footage, that he wasn't just "making his way home". Saying that, the violence used sickened me at the time. Police are often put into awkward situations like this, where they have to make a judgement as to what they should do. I suppose they thought that if flattening the pissed up Millwall bloke would help, it was the right thing to do at the time. They can't ask for your medical records before dealing with you, after all.
This story suggests he wasn't even employed as a paper seller. If I recall correctly, the original statements about his life were quoted in the Daily Mail (so no surprise there then).