I think it is okay to evaluate options and ask for input, however I do believe the CEO was mainly concerned about the quality of an employee that the candidate would be.

It's pretty obvious that the candidate was primarily interested in working at Google, and that's not a bad thing. It's pretty obvious that the candidate considers this first job as the first step in a career path toward Google, and that's also not a bad thing. The candidate asked for career advice based on his or her opportunities and goals, and again that's not a bad thing. The candidate had very little interest in actually working for the company and was already making plans to leave asap, furthermore the candidate stated all of this in a public forum without much regard for protecting his or her anonymity, this is what was bad.

Think about it from the CEO's perspective. You found someone that you feel confident investing time and money into bringing them in a training them. As CEO it's reasonable to assume some of the qualities you look for in an employee are dedication and honesty, but unfortunately you had to find out through the internet that this person actually doesn't care about your company, and has their eye on several other companies that they'd rather be working for. I imagine someone like that is not going to be a very dedicated employee. Something tells me there's a good chance that person is going to use considerable company time sending out resumes to Goggle and Apple. So as CEO, would you really want to invest the time and money into training someone knowing that they don't really care and will jump ship at a moments notice? I sure wouldn't and I'm not surprised that this CEO wouldn't either.

I'm not saying that you have to be 100% committed to your job at all times good or bad, and they say the best time to find a new job is when you already have one so I don't think it's terrible for someone to explore other opportunities even though they already have a job. But I do think that it's very reasonable for a CEO to not want to waste time with someone who made it pretty clear that they have no interest in working there, and I really doubt anyone has the grounds to sue anyone over this.