This seems like a good idea to me. People are far too unaware of what is in the food they are consuming and I certainly don't see any harm in increasing awareness. It is then up to individuals to decide whether they wish to follow the advice. 

You could argue that these items should be made healthier, rather than warnings being applied, but it is not always possible to match the convenience and flavour of these long life products without these additives. 

As long as consumers are aware of what is in their food, it is up to them whether they want to continue using these types of sauces or find a healthier option - to me the problem is when people just don't know what they are eating.