Stop looking up to him. Art is subjective (personal opinion driven, not fact), just because he doesn't like it doesn't make it bad. If you keep practicing you will improve, the only person who you have to draw for is yourself, so don't let others bother you.

A friend won't tell you something you care about is bad, he probably has his own insecuities and is attempting to make himself feel better. Getting praise from others is nice, but make sure your enjoyment of what you do is your priority.

In short; just do your thing, and those with the illusion of superiority, can enjoy their lonelyness later in life with that attitude.