Is it ever appropriate to tell a job applicant why you’re rejecting them out of the gate?

There are two schools of thought on this:

1) Responding with feedback. As you said in your comment, the right thing to do would be to send a response with a form email saying something along the lines of: “Based on your application you wouldn’t be the right cultural fit. We expect our engineers to be able to (and want to) write a brief message about who they are, beyond a single line and based on your application we aren’t considering you due to this criteria.”

This would also be where you’d mention whether or not you’d consider a future application from them if they get their act together and do some research on your organization.

2) Not responding to the candidate. This lets these candidates learn the lesson on their own (and as James Linn pointed out, not every company will hold them to the same criteria).

Full question and answer here.