Okay, let's take this very slowly.
1: In pantomimes, the baddie is often called "the Witch" or indeed "the wicked Witch." The goodie is often "the Fairy", "the good Fairy" or "the fairy Godmother".
2: In Frank Baum's anti-Christian parable "The Wizard of Oz", the heroine Dorothy (accidentally) causes the death of a character called "The Wicked Witch of the East". All the Hobbits are pleased that "The Wicked Witch of the East" has died, because she was wicked.
3: In the 1939 movie version of "The Wizard of Oz", they sing a song of celebration. It is a very catchy song presumably suggested by the operatic version of "Hansel and Gretel". "The "Wizard of Oz" is the very epitome of camp. It is very much in keeping with this tone that the little people sing a funny happy song when someone dies.
4: There is also a Wicked Witch of the West and a Good Witch of the North.
5: Mrs Thatcher was an English politician. She became Prime Minister in 1978 and remained in office until it became clear that she had become insane and was ousted by members of her own party. [The neutrality of his section is disputed.]
6: She died last Tuesday.
7: The Daily Mail Apocalypse Cult, with the full support of Her Majesty's Alleged Opposition, has announced that mourning is compulsory, that anyone criticising T.B.W in any way is part of "The Left" and therefore an un-person.
8: The Left, who, on this definition, represent the overwhelming majority, are not bloody having it. They felt that the singing of a happy camp song celebrating the death of a Baddie in a children's movie would be an amusing counterpoint to the compulsory mourning. They bought lots of copies of the record from I-Tunes, in the hope that the BBC would have to play it on the Radio 1 Chart Show which I understand is a bit like Top of the Pops only with fewer paedophiles.
9: The point of playing a camp happy song celebrating the death of a baddie in a children's movie is that it is a camp, happy song celebrating the death of a baddie in a children's movie. The point is not that all females or all female politicians are witches. Neither do the left, on the whole, think that female neo-pagans should have houses dropped on them. Everybody knows that wiccans do not wear pointy hats or fly on broomsticks, in the same way that everybody knows that members of the Society of Friends don't particularly like porridge.
Lighten up, for god sake, can't you. Bloody Chumbawamba use "ding dong the witch is dead" as part of the soundscape on their Thatcher album. Trying to be more right-on than Chumbawamba is like trying to be more catholic than the bloody pope.