I've noticed we all have a tolerance for our personal errors while loathing the ones in others we have mastered ourselves. I'm certainly no exception.
Not paying attention to grammer is like playing a game and ignoring the rules; it is sloppy and often rude or unfair.
You can tell something about a person by their personal means of expression.
When you speak or write you are painting a portrait of yourself and what you value. The details you obscure or leave out say as much as the ones you include.
I'm very petty privately inside my head about these things. I'm making personal judgements when somebody is talking to me. I am measuring and weighing like a butcher with a pound of pork loin.
However, I hardly ever correct anybody anymore unless I really adore them. Then I regard the correction as kindness; like pointing out a tidbit of spinach stuck between their teeth.