In my eyes, religions are most often systems of unsubstantiated dogma which have spread through humanity for many thousands of years. The number one reason for their pervasiveness is the indoctrination of children at a young age, because their parents think it's the right thing to do. This early indoctrination often robs people of their ability to break free from the belief system their taught. Their brain becomes wired to protect their faith, to never apply critical thinking as they may do in other aspects of their lives.
I believe critical thinking and the need for evidence to support one's beliefs is an important trait that all humans should have the right to be taught. You never see a cult with members who apply skepticism before forming their beliefs. Religions all started as small cults. I honestly think a secular world in which people demanded evidence for all their beliefs would be a happier and safer place. Religion encourages tribal thinking and the very dangerous idea that your ultimate truth has to be the right one, leading people to do immoral and dishonest things to promote their religion, including simply telling their children what to think, and never how to think.
Children are raised to depend on the idea that God is watching over them and that there's a paradise waiting for them if they conform, and that often leaves them too afraid to ever leave that mentality. Effectively robbing children of their ability to believe what they will using their own critical mind as an adult is child abuse- human abuse, in my opinion.
I believe the good that systems of unsubstantiated dogma do is far outweighed by the cost of tribal divisions between humanity and the shackled minds that are produced by these self-replicating memetic parasites.
I could ramble on forever, but to answer your question; my dislike for the existence of religions is on par with my distaste for all human parasites.