Why does the Reddit community at large disregard Objectivism as viable, and what is our responsibility in defense of it?

In many sub-reddits (truereddit, philosophy, etc) people display some of the worst understanding of the objectivist standpoint that I am often taken aback at how vehemently people disregard, generalize, compare to satanism, or do not know the first thing about that which they seem to hate so very much. Why the refusal to entertain an idea that is not their own? Why such hate? And do we have a responsibility to engage in discussion with them?

Edit: Thanks to all who contributed or will contribute, this has been exactly what I would have hoped for. I will now join this sub-reddit, see you all on other posts.