I don't understand what the problem was here. If you're allergic to tuna, don't order a dish that contains tuna. Substitutions to accommodate an allergy are nice but are certainly not required.
As for peanuts, restaurants serve them because they're delicious and most of their customers enjoy them. We shouldn't take this away from people just because some people are allergic. If you're allergic to peanuts, you should avoid ordering dishes that contain peanuts, not somehow expect all restaurants to avoid serving them in the first place.
There are legitimate complaints here. Some restaurants simply don't take this stuff seriously, and either don't take precautions against contamination or just outright ignore allergy-related requests. But expecting them to go beyond keeping allergens out of dishes that aren't supposed to contain them is odd.
As for peanuts, restaurants serve them because they're delicious and most of their customers enjoy them. We shouldn't take this away from people just because some people are allergic. If you're allergic to peanuts, you should avoid ordering dishes that contain peanuts, not somehow expect all restaurants to avoid serving them in the first place.
There are legitimate complaints here. Some restaurants simply don't take this stuff seriously, and either don't take precautions against contamination or just outright ignore allergy-related requests. But expecting them to go beyond keeping allergens out of dishes that aren't supposed to contain them is odd.