I'm a native speaker and sometimes my brain and fingers don't communicate on the keyboard.
But, here's the funny thing -- because of the predominance of non-native speakers, no one bothers to correct grammar or spelling. If I did that in posts, I'd be doing nothing but that on this board. Just correcting loose for lose would take all my time
But I really don't like making spelling or grammar errors. I hate it. Just because it isn't my mother tongue, I always want it to be better than it is.
This case is just silly though.
He had nothing else to point out so he picked on my mistake.