To proud dad, I dare say you have every reason to hold claim to that title, you have a son who has shown he is willing to step and do something a lot of others are not so willing to do, and many are only willing to carp about, might I also throw in there that he honours you in doing this too (he had to learn it somewhere).
As for the ones rattling about "dead trade business", I would say they're speaking from ignorance, short sightedness, or both, so I would suggest to try and let it drift. I have been in the Field Artillery for over 27 years now, and I have heard this same kind of talk about the Field artillery. . just a few years ago they were saying the Field Artillery is an obsolete idea; down grade it to a reserve function at most or get rid of it. There were a number of people even at high levels that truly believed that, only now through the lens of recent events in Afghanistan have they relearned how valuable that once dormant capability is.
As for the air defence, they are not going to get much attention in the news but what they do is of a vital importance. For right now it is in ASCC's where coordinating and vectoring the air resources into battles on the ground quickly takes considerable skill and training; it might not make for a good war story but it is part of what is needed so that the ones in direct contact with the enemy get the response they need in short order.
As for the future, who really knows? Besides the domestic 9/11 air defence scenario, one item that General Leslie (Chief of Land Staff, or general of the Army) has referred to more than once, was what happened to the French forces deployed to the Ivory Coast in 2004.
http://www.cnn.com/2004/WORLD/africa/11/11/ivory.evacuation/index.html
http://www.themilitant.com/2004/6843/684303.html
Basically the French forces were "accidentally" bombed by the Ivory coast air force, and the french retaliation of attacking with their own air force was seen as an over reaction, not proportional to the threat, and was used as a pretext to escalate the situation by many belligerents involved; critics of the French response did seem to "allow" that they were entitled to self defence though, i.e they should've had some kind of air defence capability. Kind of sounds like blaming the victim for not being able to adequately protect himself to me, but then again nothing should surprise me when it comes to politics and UN missions.
What I'm getting at is there may well be situations in the future where Canadian forces, deployed in a similar Ivory Coast type mission way, will very much need protection from such "accidental" bombing and have at least a credible self defence from such a threat, and the presence of that force cannot be one that escalates the situation; this protection will most likely come from Land Based Air Defence. Your son may very well be one of those in future standing up to provide that protection.