1. "That is an unregulated currency, therefore that's illegal!"
2. "Imagine a ball thrown in the air, at first it will go high but then eventually it will crash. That's the same logic that bitcoin has."
3. "Use bitcoins? No! That's for crazy people. I'm a normal one so I use Paypal.. But then again you've given me a valid argument so I'm going to use my previous 'Bitcoin is used for drugs' reason for this one."
4. "Bitcoin would fail, okay? No more questions asked, Jimmy! I don't really understand why so I would just keep talking. I don't care if you guys don't understand because I don't so just listen and believe me. M-kay?"

But seriously though, I think the teacher was kind of right with number two. No matter what product, currency or whatever that is, that's doomed to have an end. Maybe other things are meant to crash sooner than most, but everything will crash eventually. Although I also believe that the teacher only did look at the bitcoin chart somewhere and then analyzed it.