Well here's the thing. One is a complete liberty to stand up and voice dissent against the governments decisions/action and what have you. One is even completely free to say that the CF is a group of human rights abusing barbarians that must be opposed. That is actually well within protected speech. There are some things that are not protected, these things which indanger the common good and public safety. There is a very specific reason this is mentioned in the criminal code of Canada. (twice infact, for varying degrees of severity)
Every army requires discipline in order to function. If commands are simply not followed, an army comes to a thundering stop. This is similar to what would happen to your body if the nervous system simply shut down. By trying to entice soldiers to disobey lawfull authority, you are infact trying to render impotent the democratically elected government. If you have a problem with the governments policies, write your MP, don't harass those who's duty it is to follow orders.
If we allowed every political movement to dictator to be to speak directly to the armed forces and freely allow them to 'seduce' the troops, we could end up like most other countries that are enthralled with civil war. This is a VERY old law, and although the conditions that would require it to be paramount don't exist (I doubt we'll have dissention from this letter) it should still be enforced. The law is the law. (and yes respect the idea that the best tactic would be to ignore them, joke about them, basically render them meaningless. However, I see serious political advantage for raising this - it will expose them for the tendentious group they are while showing some of the grief CF members put up with.)
Additionally, soldiers have a right to not be harassed because people disapprove of the government's policies. Walking down the street getting called a baby killer after getting spit on, or receiving a letter about how you, and people know care deeply about, support human rights abuses - and that you should disobey your chain of command, it is simply harassment that soldiers should not have to go through.
:warstory:
edited for a typo