That's pretty interesting, what sort of people have you discussed this with? I'd imagine that many people in the center and leftward would at least try to inject some nuance into such blunt statements.
Care to list the reasons illegal immigration is good?
Well, one that immediately comes to mind is an asylum seeker. Whether or not a country is willing or able to accept this person is, in my opinion, secondary to that person's immediate safety. I would hope that that person would be a well-behaved resident and go through the proper avenues to get documentation. In the meantime, I would consider their illegal immigration a "good" thing.