In the halachic responsa this past Shabbos the question was asked if its a mitzvah to eat meat at the Purim seudah. We had learned that it was and when I showed this to my Rav, Rabbi Yehuda Pfeuffer shlita, he asked me to write to you. This is from his hand written note (please excuse me if there are any errors in my writing as the hand written note is a little untidy!) “The Mechaber in 696 states that an onen eats meat on Purim Midoraisa. The Magen Avraham questions yet doesn’t argue, see Emek Brocha, Elia Raba that it is a definite chiyuv on Purim unlike Yom Tov according the Magen Avraham.Therefore there is no source for the psak to not eat meat !”
The halachic responsa you mention (here) notes that there is an obligation to eat meat on Purim.
However, it adds that somebody who does not like meat, or for instance a vegetarian, doesn’t have to force himself to eat a food he doesn’t like.
Of course, for such a person, for whom meat does not provide any simcha, the concept of eating meat will not apply. In spite of the interesting analysis of the Emek Berachah, I have not seen anybody prohibit vegetarianism on account of the Purim Seudah.