I'm always amazed that such a proportion of European publics are so vehemently averse to asylum seekers. There's some anti-immigrant sentiment in the US but almost all of what I've heard is about illegal immigrants and a lot of the time (in New Mexico at least) it comes from Mexican-Americans. Disliking freeloaders I can understand, but asylum seekers aren't so much seeking to cynically exploit the system as they are trying to not die and asking the government to evaluate their claims to being in immediate danger of death before deciding whether or not the sword of Damocles is of the appropriate size and shape to permit approval.
Then again I've got a nagging suspicion most of the mob members are on the dole themselves, which is how they had the time and incentive to form a mob. They won't think of asylum seekers as a drain on the system so much as competition in the race to drain the system.
I could well be getting a lot wrong here, but these are my general and preliminary impressions. In any case, good on your public for stopping a mob.