For evidence of how supportive tech communities are, take a look at what happens when someone tries to show off their early projects: https://news.ycombinator.com/item?id=8747053
Comments include "They're probably lying," "This is like a parent posting their kindergartener's first crayon house-and-trees-and-sun drawings out into blogs," etc. And most of those comments were heavily endorsed by this community, judging by their overall position relative to sibling comments. So if HN is a thermometer for how friendly tech is, apparently nice people are rare.
Hopefully the culture will change, but that will take a lot of time.
(Now that I've posted this comment, I realize that it's not very supportive, which is a little ironic. Maybe a post-it note on my monitor that says "Be supportive!" would be a good reminder.)