Well, so far I haven’t found evidence that they were yet thankfully
One of the states they settled in (Connecticut) abolished slavery in the late 1700s as it was already uncommon by then.
I found an old man’s description of the original meeting house founded by my 10th great-grandfather, and they had a separate section for black people but they were welcomed there, even if some of them were slaves. [some were slave, some were free]. Liberal even back in the 1600s!