Misuse of English grammar used to bother me a lot. But not anymore.
Teaching English and living in Japan has taught me to be much more relaxed about it - if I wasn't, I would have a hernia. Now I merely chuckle at what would have made me fume.
Trust me, there is nothing quite like regularly seeing mistakes that completely twist meanings. All the trains will tell you that "There are no exits" (Meaning "This door is not an exit" rather than "You will never leave this train! You are trapped! Mwah-ha-ha!") and learning to decipher what final year high school kids mean by "curry eyes" and other joyous phrases, or what movie they are talking about when they give a description like this "This scene is a great battle. I am going to kill two people seriously. reconcile. cooperate and fight against an enemy with two people." (grammar is not too bad there) or this "chihiro. sad to kamagi that is want to work stout heart. metamorphosis on back chihiro to recall habu is real name. many pig among to discover my parents."
Now, I know that its different for second language speakers. I know it is more difficult, but I find that by getting used to that as a general level of English in my life, I really don't notice native speakers' mistakes either.
One thing I will say though, when official boards (like the board of education) gets it wrong, it does bother me (or result in hysterics, depending how amusing the mistake is - an elevator labeled 'erebator' in an airport is just embarrassing). At least get a proofreader.
But to lighten the mood, brought to you by the Ministry of Education...