Just in this topic there is several commenters that take exactly that position. There are many more. Of course, not every person who opposes immigration restrictions is for open borders, and not every politician that is ultimately for open borders would think it is a good tactics to proclaim it right now. But proponents of unlimited (and essentially unlimited - i.e. guarded by checks that anyone with two brain cells can pass or limited by mechanism that lacks enforcement in practice) immigration obviously and prominently exist. You can see people with slogans proclaiming that on any pro-immigration protest. Surely, not everybody thinks so. But denying that there are many people saying so is denying the obvious.