The first quote wasn't an ad hominem attack because it wasn't directed at the engineering deans, but rather at the author. If you're trying to determine whether people should drop out of school why would you only survey deans to make a point? Moreover, it is perfectly valid to note the conflict of interest a speaker may have. Their incentives don't make their arguments wrong, but it should give us caution before making generalization or relying on their expertise.

I think we're talking past each other to a certain extent. The deans do make some good points. 1-4 are generally true. I just don't think they are sufficient evidence to show that students shouldn't drop out. They are saying that colleges are good social networks and send important signals to employers. My argument is that something is wrong when we are spending 100K on a screening/networking mechanism. Notice that none of the deans said stay in school because of the things you'll learn in the classroom.