I despise Oracle, and I think there aren't many companies out there as evil as them. I would be thrilled if they burned to the ground, figuratively speaking of course.
But that said, I think it would be dumb to jump to conclusions just based on having Oracle on the resume. You should at least ask them why they worked there, and why they left. For all you know, they had no idea how bad Oracle was when they started, and they left because they saw how evil they were. That is the exact kind of person that I do want to hire
I guess I consider it part of one's ethical duty to research the places you work and decide whether you are willing to put your life's efforts behind supporting the company's behavior. Oracle very famously attempted to completely undermine how the entire software industry works and make unapproved interoperability illegal with their Google Java lawsuit[1]. If an applicant supported the company that filed that lawsuit by working for them, and doesn't feel enough shame to leave it off their resume, then I don't want to work with that applicant.
But that said, I think it would be dumb to jump to conclusions just based on having Oracle on the resume. You should at least ask them why they worked there, and why they left. For all you know, they had no idea how bad Oracle was when they started, and they left because they saw how evil they were. That is the exact kind of person that I do want to hire