Before I remind you of how Elly reacted, let's see how a regular, normal, sane human being who actually understands how life, the universe and the business world work is going to react to the prospect of a college sophomore embracing his inner Wille Nelson. He or she would, I should think, react as follows:
What do we have here? Heh. Just another arts major going all bohemian on us to freak out Mommy and Daddy. That's fine when he's in school but he's not important enough to stand out from the crowd so he'd better cut his hair, shave and get into a business suit like the rest of the drones if he wants to play in our sandbox.
As it happens, that's exactly what does happen to him when he applies for a job in the real world. I would be fine with that were it not for the depressing and awful fact that Elly manages to turn that into some kind of victory for loving motherhood. This is because her reaction to Mike's letting his outward appearance more closely approximate the person he really is is one of sheer idiot moral panic. What makes Elly react in the terrified way she does is not that she doesn't get that Mike doesn't want to get carded everywhere he goes. What makes Elly react the way she does is that she believes the following absurd idea:
Oh, no! What has University done to him that he totally turned his back on everything good? Why is he following down the same road as that beatnik Phil? Why do people DO that? Don't they know that their pooooooooor mothers love them and don't they care that they're breaking my heart? What HAPPENED to my BAAAAAAAAAAABYYYYYYYYY????????!!!!!!!!!!
The idea that Mike is still the same unpalatable clod she goes out of her way to not understand because that gets in the way of her living through him and off of him is not one Elly can fathom. Doing so would mean facing the terrible idea that she's a superficial jerkwad who doesn't know crap-all about anything and that would be just terrible.