You're absolutely right. We have no credibility, because we take a double standard.
These two courts are, as you said, two of the only mechanisms that can be utilized to seek justice in the situation in Palestine, and not merely for Palestinian victims but also for Israeli ones. It strikes one as incredible that the Government of Canada would utilize those mechanisms, the ICC—indeed, Canada was at the heart of the creation of the ICC—and the ICJ, now, in matters concerning Iran and Syria, yet deny the option available for the people of Palestine and other victims, including Israelis, to utilize these mechanisms. The message this sends is that no, you may not resolve this conflict through pacific means and, by the way, if you're Palestinian, you can't use violence at all to end the occupation of your territory, now going on 56 years. Occupation is meant to be a temporary circumstance. This one has lasted generations.
If you can't use violence and you can't use non-violent legal means, what else is left?
This goes to Canada's credibility on the international plane.