As per a recent comment this thread is meant to voice contrarian opinions, that is anything this community tends not to agree with. Thus I ask you to post your contrarian views and upvote anything you do not agree with based on personal beliefs. Spam and trolling still needs to be downvoted.
Open borders is a terrible idea and could possibly lead to the collapse of civilization as we know it.
EDIT: I should clarify:
Whether you want open borders and whether you want the immigration status quo are different questions. I happen to be against both, but it is perfectly consistent for somebody to be against open borders but be in favor of the current level of immigration. The claim is specifically about completely unrestricted migration as advocated by folks like Bryan Caplan. Please direct your upvotes/downvotes to the former claim, rather than the latter.
Collapsing civilisation as we know it is presumably not a bad thing if you think that our current civilisation is fundamentally unjust or suboptimally allocates resources based on arbitrary geographic boundaries.