Religion has rules. if you want to be in a religion, follow the rules. The bible clearly states that woman are not supposed to teach men in church. You may obviously choose to interpret that as a cultural or time-sensitive thing, or say that the bible gets things wrong, but it is not unreasonable for a man of God who believes in the literal bible to take the admonition seriously.
After all, it shouldn't be impossible to find enough men to teach the men that we are FORCED to have women teaching them. This isn't some onerous burden.
And yes, my church will not have a woman teach men. They can teach children, but not men. And our entire denomination doesn't allow female pastors, elders, or deacons (although I think some churches have female deacons).
I think the operative words are "in church." To me that means from the pulpit, not down in the basement or the annex, teaching Sunday School. If that was a problem, then maybe they could have found a gentler way to deal with it.
The pastor's statements reads: "relieve a member from teaching an adult class". So it seems she was not only teaching women; she might have had a co-ed audience and that is why it was unbiblical.