Why do I come across as argumentative when I don't mean to?

You're probably doing something engineers are trained to do well: spotting the weakest point in a statement and addressing it immediately. Among engineers that's normal, it's how you pressure-test an idea. Outside that group, jumping straight to the flaw reads as combat, because most people expect acknowledgment before critique. Skip the acknowledgment and the correction, however accurate, sounds like an attack.

The fix isn't to stop noticing flaws. It's to add a step before you name one. Mirror what the person actually said, in your own words, before you respond to it. 'So you're saying the delay is coming from the vendor side, not our processing' shows you took in their point accurately. Only after that does your counterpoint land as a continuation of the conversation instead of an interruption of it.

The other move is 'tell me more.' When you jump to the flaw fast, you often skip real information the person hasn't said yet, the constraint, the deadline, the thing they're actually worried about. Asking them to keep talking, before you weigh in, gets you that information and signals you're listening rather than waiting for your turn to disagree.

Both moves cost you almost nothing in accuracy. You still get to make the correction. You just make it second instead of first, and that ordering is the entire difference between sounding argumentative and sounding sharp.