1) Fear (of unknown, of something different, etc.)
2) Media washed our brains with "terrorists" and whatnot
3) Fear (yes, a LOT of fear going on)
Pick whatever you like. They may be more reasons, ofc, but most people label things (and people), thus putting many into the same basket. Which is more often than not FAAAAAAAAAAR from correct, fair and optimal.
But, in today's world, compassion is severly lacking, so no problem.
Also dealing with such cases of mass immigration should be on case by case (person by person) basis. Unfortunately, many just label them "immmigrant" and look at all of them the same.
They don't even stop to think "Wait a minute...why do I think that Doctor/Scientist is the same as that thief?" (Cause, you can bet your ass, there will be both kinds of people like that)
Why am I writing this? Honestly? I have no idea. Too much time at work atm, so even though this posts means nothing....oh well.