This exactly. At my current employer, I feel I can oppose pretty much anything my managers tell me - technical or non-technical. I can say "I disagree because

This exactly. At my current employer, I feel I can oppose pretty much anything my managers tell me - technical or non-technical. I can say "I disagree because X", and the reply might come back as "OK - that makes sense", "Let's discuss this in more depth because Y", or "I'm going to overrule, you must do Y". If you have a functional relationship with your managees, they need to know they can disagree with you and that you know you're fallible and just need it pointed out. I always make sure that when I give technical feedback to others (whether higher or lower 'ranked' than me), they can come back and argue any bit they disagree with, and so far almost everyone has at some point.