This is a problem with your stance in my opinion. Where is the line?

The distinction between doing something in an official capacity as a representative of the government and doing it as a private citizen is a pretty well established and easy to follow distinction.

Can I post a picture of me in my uniform on Facebook with the caption "Trudeau/O'Toole is a traitor that has to be stopped" as CAF member?

No, because that would be a soldier - an agent of the government who has a duty to be apolitical - engaging in politics. You are not speaking with your own voice when you present yourself as a soldier in uniform, you're speaking as a representative of the government. You do not get to superimpose your personal political opinions onto the military by expressing them publicly while in uniform.

This is a problem with your stance in my opinion. Where is the line?

Do you seriously not understand the distinction between doing something in an official capacity as a representative of the government and doing it as a private citizen? Because it's a pretty well established and easy to follow distinction.

Can I post a picture of me in my uniform on Facebook with the caption "Trudeau/O'Toole is a traitor that has to be stopped" as CAF member?

No, because that would be a soldier - an agent of the government who has a duty to be apolitical - engaging in politics. You are not speaking with your own voice when you present yourself as a soldier in uniform, you're speaking as a representative of the government. You do not get to superimpose your personal political opinions onto the military by expressing them publicly while in uniform.