I`ve never seen anyone calling it "investment" so far. 
Neither have I, and I totally agree with what you said below:
People will continue to see btc as an investment opportunity.... You can`t stop them from buying bitcoins.
It's volatility and sometimes uncertainty coupled with anonymity make people see it as an investment opportunity.
There is freedom of speech and opinions, you can`t create censorship.
The freedom of speech, I guess, was one of the factors why we have this post here, after all, wasn't it?
Good points, guys. Who can stop calling it investment? Why would they?
The American Heritage® Dictionary of the English Language defines an "investment" as
property or another possession acquired for future financial return or benefit. So, what should we call BTC then?