Well, the position of conservatives on immigration is governed by several factors, one of them is their negative stance on ethnic minorities, but also they want to please big corporations by constantly growing the pool of skilled labor so companies can hire at a reasonable cost. Of course the first choice to fill the labor gap is natural population growth (more births) and the second is immigrants from Europe, but these options are beyond the control of the Canadian government, so they have no choice but to go for the third option: accept immigrants from other countries.
One last point about Chinese immigrants. They, unlike many other ethnic groups, are known to integrate pretty quickly (change their names, go to church, interracial marriages, etc.) and thus don't pose a cultural threat from the conservative's perspective.