Ehh, I don't know why that sign would offend anybody that can't speak English.
If one can't speak the language, it's a fair bet they can't read it so how could they know that discrimination is occurring?
One of the things that made our nation great was the fact that brave people had the courage to leave their homes and plunge into the unknown because they knew they had a chance to better themselves. That moxie built a nation. But at the same time, they had to assimilate and do what was needed to do in order to succeed. Many did. Many did not. Learning the language was forced on them. They did not whine about it, they just did it. They had to learn the language in order to succeed. That did not mean that they had to deny their roots, their original language or anything else they brought to our melting pot. When you mix in many good ingredients, you get a good dish.
Those that promote the notion that learning English is not necessary demean and diminish those immigrants they claim to speak for. By not promoting a common tongue, they are indirectly saying that immigrants are too stupid to learn our language. Well, most of the immigrants surmounted difficult odds to get here. Learning the language is just the next step, and most, if confronted with the reality, would knuckle down and do it, to their betterment. It would be better if the bleeding hearts would mind their own business. It would also be better for them to remember our national motto. Out of the many, one.
Oh, by the way my maternal grandparents were immigrants from Lithuania. My paternal great grandparents came from Germany and Scotland. They not only proudly learned the language to the best of their ability but their children spoke English with no accent. One fought in the Civil War for the Union and was a wounded veteran. His son became a pattern maker and helped design and build the patterns for the Cord automobile as well as having an impact in the fledgling auto industry, who's son was a decorated combat vet and POW in WWII. Another was a shop keeper and grocer who helped build a neighborhood of immigrants into an American neighborhood, who's daughter had one son who was a policeman and then businessman and another who is a printer. Another daughter who had sons who are priests and postal carriers. And the story continues.
My two cents is that the owner of the restaurant is doing a favor for those who can't speak English. Learn the language and you'll be better prepared to take advantage of the opportunity our country offers. In this case, a good steak.
PS: I'd be willing the to bet that the immigrants who won't learn the language, who refuse to assimilate didn't actually get here legally either.