No, see, it's dumb things like that that I count on my readers to find for me before I ship it off to editors. I'm NEVER offended by someone catching a grammar mistake or a typo, I'm grateful. And I'm always thrilled when I see that you've commented on something I've posted for crit, because I know that you're a good, thoughtful beta reader and your comments will be valuable.

A writer who gets offended by people pointing out his mistakes is way too invested in his own ego. Especially if they're real mistakes and not just matters of opinion.