Hang on, the advice given is not "do whatever makes you happy and productive.", the advice given is "never use Python 3 until every line of Python code on your computer is written with Python 3".

And please explain why to ignore people who say Python 3 is the future, I don't understand why.

I thought you were asking me a (loaded) question. The advice given was not "never use Python 3 until...", that was a suggested reply to people telling newcomers to go for Python 3. Perhaps too tongue-in-cheek, but coming from someone who taught millions of people Python, worth noting.

You ignore people who say that Python 3 is the future, because it will make you happy and more productive when you can run modern libraries that have a 2.7 requirement. Or you don't ignore them, and get into endless debates about how almost all libraries support 3, and that you need to spend just 1 in 20 days of your time worrying about getting your code to work, instead of... programming. But if that makes you happy, you should do that.