The commonality in both your and the parent's situation is that you reacted defensively. Your response was "You destroyed my tabs!" when a proper response would have been to try and understand your coworkers motivation. Perhaps he had some really good arguments for preferring spaces over tabs? Tabs can be problematic in heterogeneous environments where developers with different tab settings and different editors work on the same codebase. Have you read the arguments in Google's coding style guideline?

Maybe your coworker was a fucknut that did it just to mess with your code. I wasn't there so I can't know. My point is that you shouldn't assume that.