You talk about others having a mental disease. It seems that you are completely obsessed with anger at anyone who expresses a desire to have a tattoo. That obsession seems abnormal to me and worthy of seeking medical help.
My niece had a boyfriend for about a month the when she was 16. He got killed in an auto accident so she got permission from her mother to get a giant memorial tattoo that covered half of her back with his name on it.
Before the tattoo was fully completed she had a new boyfriend. She moved on, but the tattoo was here to stay.