I suspect that most people would have little animosity towards the little old lady, suffering from dementia, that Russell Brand talked about in his recent article.
People who are not admirers of Mrs T are responding to their memories of how she behaved when she was in power, to the repercussions still being felt today and to her influence on current policies.
It seems fairly evident that, whilst there is a large amount of support for Mrs T, there is also a significant number of people who believe that her policies were divisive and damaging. So, she can't really be considered to be a generally "uniting force", as Churchill was, and some people feel that the lavish funeral arrangements are therefore inappropriate. In addition, the unprecedented attendance of the Queen, who is meant to be politically neutral, is seen by many as providing tacit support to past and present Conservative policies.
Personally, I think it's spiteful and stupid to jump around "celebrating" anybody's death, but I do feel that people should have the right to express disagreement without being called "nasty hate campaigners".
Nothing that is said can hurt Mrs T now, but, as Lilygran said, it was her own party that plotted to overthrow her and it was they that made her cry when she was alive.