St Patrick was born in the UK to a non religious family, and as such, by the Roman Catholic Churches Canon Law of the time - being as that he wasn't Christian, it was acceptable for him to be taken as a slave. He was taken to Ireland where he was forced to work as a slave for the Roman Catholic Church, who were at the time trying to spread their influence across the whole of Ireland. While he was there he was abused and brainwashed into believing that if he didn't convert to Christianity he would go to hell.
He apparently had a religious experience while there and converted to Christianity (according to the RC version of things), and then was allowed to return to the UK to take up his training within the Roman Catholic Church, where he eventually became a Bishop.
He then returned to Ireland and set about trying to convert the Serpent Bloodline tribes that were still living there. The ones that wouldn't convert he helped to murder or drive out into Scotland.
The Serpents he drove out, were the Serpent Bloodline families, and NOT Druids like so many Christians tell us in their stories. They might have called our people Druids, but they were not led by male Priests. One of the main reasons for them trying to convert us or murder us was because the females were the Spiritual and tribal leaders. They would never admit this in their his-story books.
So celebrating St Patrick's Day is celebrating the murder of our people, hunted down and forced to either convert or die.
Why would anyone want to celebrate that?