I am an overthinker, and I know that ideas are cheap; they're driven as much by emotion as thought, and if my observations are not received in the intended spirit, it's not necessarily worth it to keep pushing.

What has consistently helped in winning trust when providing feedback is pairing any concern with either a qualification (blocker/aesthetic/security), a solution, or both. Then, you not only expose the thought process behind your perspective that they've missed something - with which your audience may not agree, but can judge in earnestness - but also your intention to help and support their vision.