Why should corporate interest support these trolls? Reducing immigration would cut down the influx of cheap labor and result in wage increase across the board - which is against corporate interests.
I think that the low support for these crazies is a result of corporate opposition and thus bad press, because a lot of people in this country actually sympathize with their views, they just feel uneasy to participate in groups and events labeled by the media as being outside mainstream and fringe. Nearly 60% of the US population thinks that illegal immigration hurts the economy, about half think that legal immigration should be decreased http://www.npr.org/news/specials/polls/2004/immigration/?sourceCode=gaw
In other words, the minutemen and kindred trolls simply demonstrate in public what mainstream US-ers think privately. The fact that these trolls do not get much public support is due mainly to the negative press they get and the general lack of involvement in anything on the part of the mainstream population.
Wojtek