Of course the British Columbia College of Teachers found another excuse to condemn the teacher's published statement. The teacher wasn't innocent and found guilty of any crime. He wasn't innocent and found guilty of any crime he might commit. But he was guilty of advocating thinking that runs contrary to policy.
Whether or not negative population growth is a declared policy, that policy is intruding on each human's choice for their posterity everywhere. And on even what they choice to say even though they don't know how what they said should raise such a ruckus.