Those who are working on themselves and passionately striving toward their dreams are too busy to stop what they're doing to criticize others.
On the other hand, those who are too insecure or afraid to follow their own dreams have all the time in the world to sit around and criticize others who are following theirs.
It's very easy to sit around and judge others; it's really hard to focus on improving yourself and work toward your dreams.
The person who has the courage to take the leap and put in the time and effort required to make their dreams a reality is like a mirror to the person who doesn't have that courage, a mirror that amplifies their own fears/insecurities.
For people like this, their first reaction is to try to project those emotions upon people who are actually following their dreams through criticism and judgement.
When talking about your art and your career with others, always know who you're talking to and where that person is coming from.
Those who can, do. Those who can't, criticize.