From a social justice perspective there couple of different layers to consider, but from a simple standpoint of MEC's model demographics compared to the demographics of the country then yes the catalogue and MEC's advertising do not reflect the demographics of Canada correctly. I say that without having looked at the catalogue and simply going off of memory of their adverts I've seen.
If you consider the activities that MEC sells gear for, I honestly do not find it surprising that their advertising tends to focus on the white and often male demographic. One only really needs to look at participation in those activities to understand why this may be so. The real question though is why these activities tend to be over represented by the white and male demographic. A few answers spring to mind. One of course is monetary as many outdoor sports require deeper pockets to participate in. If you look at the demographics on poverty, people of colour and women tend to be over represented compared to the population as a whole. Another factor is cultural, as many of these activities tend to fall more into the cultural domain of whites. Note that there is probably some crossover between the cultural and poverty factors as well. A third answer would be biological. Many of those activities tend to have higher elements of risk and adrenaline, both factors associated more closely with male behaviours. So when you consider those factors, it becomes less of a surprise that these activities tend to have higher participation by white males. So now the question becomes is that necessarily a bad thing?
So in terms of social justice and equal representation what should we be doing? Does it make sense to over represent advertising demographics with backgrounds that do not accurately reflect the participation of the activities? A simple answer to that is yes. A slightly more detailed answer is that one of the reasons often cited for lack of participation in a particular activity is a lack of sufficient role models, and this is something that can cut across ethnic categories. So by MEC working to improve the full representation of Canada's demographics into their literature or even boosting the profile of minorities it goes a long way to helping those people realize they have a place in outdoor rec. So I'd say good on them and good for making an announcement of it to bring attention to the issue even if it may seem to be a bit of a marketing play as well.