I know of a simular situation, also with a so-called "conservative" speaker. It occurred here in Texas. I was a member of the church board. In that case, the Texas Conference did not tell us we could not allow the speaker to speak. I am not sure they have the authority to do that. However, they officially discouraged us from allowing him to speak. We had a board meeting and agreed to follow the Conference recommendation.
I will say that I do not like labels of "conservative" or "liberal." I think more descriptive labels are better like one that spreads conspiracy theories, anti-trinitarian, anti-vaxxer, legalistic, doesn't believe in the Spirit of Prophecy, believes the church has become Babylon, etc. I heard Steven Bohr preach a few years ago. I don't recall his message but I do recall being disappointed. I had hoped to hear someone more inspiring. I was at an event where I was running a booth to promote Adventist Recovery Ministries.