Hinduism is a threat, but not for the reasons they claim. Hinduism encourages tolerance and discovery, it is a living religion that grows and changes with the times. Hinduism makes sense. It encourages you to find your own way. It teachs that we are all beloved children of God, not just a select few. Hindus preach love, and for the most part, they actually practice what they preach!
This constant open mindedness goes against everything christianity preachs! Christians are taught that they are superior, that thier over simplified dogmatic religion is the only true way. Hinduism challanges that view point and scares them!
The youth of today are no longer willing to believe in what mom and dad do just because they say so. Kids today want to know "why" and "because I said so" is no longer an acceptable answer. So these kids go looking for a religion that makes sense, and thier parents are scared to death thier kids will find Hinduism, like I did.
All this scares the religion that only has dogma, bigotry, self righteousness, and hate to offer.