I'm mostly a vegetarian except that I do take molecularly distilled fish oil. Very simple way to get some of the health benefits of seafood consumption but take no risk.

However, I actually feel mercury isn't nearly the bugaboo that vegan proponents often make it out to be. High ocean mercury levels have been a thing for over 100 years. Yet a great many studies have found seafood to be beneficial to longevity and overall health.

All of your points sound like vegan talking points, but to each their own.