Someone posted "why do they [Jehovah's Witnesses} feel they have to go around ‘converting’ people?" Actually, that is what ALL committed Christians ought to be doing - giving others the chance to go to heaven, as they hope they themselves will when they die.
It was part of the faith from the very beginning, and all denominations sent missionaries to the "heathens" to try to convert them. If you can be bothered to read the books of the New Testament, there are lots of Letters to the Corinthians, Letters to the Thessalonians etc etc where St Paul writes to keep the missionary groups up to date and encourage them in their work. They were pretty successful too, converting a good chunk of the world's populations.
The JWs are only carrying out what they see as Jesus' instructions. They also do good work looking out for old and ill neighbours, and chatting to lonelt pensioners. If they don't want to join their congregation, that is OK, but they see visiting them as pastoral work. They don't deserve rudeness or curses, Just say you have your own denomination (or none) and don't want to discuss it with them,
Incidentally, how often does the vicar/minister of your local parish church visit non-members in the parish and chat to them - have you ever met them? Or even visit signed-up members of his/her congregation?