Yes because it's a lie, although theism has consoled many people it has detached them from reality and the truth. Reality is far more beautiful than any theist book will have you believe.
No. Theism gives people hope that everything they have worked for will mean something, that dead love ones are not really gone forever. There is absolutely nothing wrong with that, people need something to believe in. But at the same time, people can take their believes to far, keeping human progress to a minimum, which is an occasion it can be harmful.
Of course some good things can come from theism, but many literalism's/extremists cause a great many problems in the world. Are there good Christians, Muslims etc. that contribute to society? Of course. Are there bad ones that continue discrimination and hate? definitely.
Not really. Many people find comfort in religion. Personal faith is not a problem IMHO.
The problem is when they affect social and scientific progress in a negative way, but that's typically more of an organized collective effort than the personal beliefs of individuals.
Of course, I find no comfort in religion personally.
I think theism helps some people and can also give them hope when their lives seem otherwise meaningless. Some people need to have spirituality just to cope with a mundane or depressing life. Aside from theism, I think religion could instill positive morals and give a sense of guidance to people who do not have them. I guess believing in inane concepts can help people form a purpose out of life. If only people were more sensible about it.