I'm not an absolute expert on food...but I'm pretty sure tuna is not a vegetable. As a jew, I don't really think it's rude, as you don't expect kosher food in a non-kosher restaurant. Same with Muslims and Halal. Therefore, I don't think this particular bit is too valid. However, the rest of what you say makes me want to run from this place...typical tourist trap...if you want a french bistro in a touristy area, that actually has decent food, I can suggest Luden on Spuistraat, they have an excellent fish soup, which perhaps your 'vegetarian' wife might like.