If an employee is granted the power to make that decision based on the information they have at hand, why can't they make that decision?

I don't know about the internal process behind Air Canada, but I would hope that they would have some type of thorough review process with the GA and the passenger for all of these incidents where a passenger had their BP voided because there is a high probability that they may be disruptive on the flight, and if the GA can adequately justify the decision they made with the information at hand, I honestly don't see how it is considered abuse of power.