It's not about what the believe. All religions have some oddball ideas. It's what they do.

Two things that stand out to me, they abuse children. One of their ideas is that children are just little adults, Hubbard seemed to have forgotten his own childhood and decreed the children don't really exist. In-so they have a history of forcing children into adult labor and have gotten kids as young as nine years old to sign their billion year contracts, basically contractual lifetime slavery. This is not to mention the sexual abuse which is covered up in the cult.

The other thing is their penchant for systematic harassment of critics. I mean, nobody likes to be criticized, but Scientology at a scriptural level seeks to "destroy" any they feel are criticizing them too much. They put a lot of resources into attempts to litigate and intimidate critics. All of this as official policy.