If i was in it for morals, then id tend to agree. As it is im allergic to some meat, and just dont like the other stuff.
Saying im a vegetarian simplifies it all down to the stage where they wont serve me meat, stops a massive questioning about how hypocrytical it is to eat fish but not animals too.
If im buying food im looking for a "vegetarian" logo, because that overlaps 99% of my diet, the term for a vegi that dosn't eat meat is a "pescetarian". How often do you see a pescetarian option on the menu ? If anything blame society for effectively labelling me incorrectly.....rather than accuse me of being a liar.
Fish are animals. If you want it to be more widely known then start using the term rather than calling yourself something that you aren't imo.