Bad form. Really bad form.
Yep. And before anyone bashes Dubai, let's remind ourselves that having sex on a public beach, ignoring warnings to stop and then verbally abusing police officers will get you arrested pretty much anywhere in the world. If this happened in America, everyone would be praising law and order.
In the service of my country as a sailor in the U.S. Navy, I have had the pleasure to enjoy Dubai on several occasions. It is a wonderful city and I don't have a single complaint about the place. In fact, Dubai has been so far my favorite port. I look forward to returning again.
I can personally attest that one can get as drunk as they want within the confines of the numerous hotel night clubs. Furthermore, if one wishes to enjoy the company of the opposite sex, again, this is fine as long as it takes place within the privacy of the clubs or a hotel room. Dubai (like many American cities) takes public drunkenness and public sex acts seriously. This couple weren't in a club or hotel room. They were outside at the beach and not being discrete whatsoever with their activities.
Keep the drinking and PDAs in the clubs and nobody in Dubai will bother you. Take it outside in front of their children and they're going to get understandably upset. We'd react the same way.