He already had Xochi and twelve other headmates.I have a strong hunch that Phil is basically using his deer plush like Cartman uses his dolls and plushies in South Park: to have the perfect friend, one who will only ever say good things and never call you a fat re.tard.
Phil in a high, squeaky deer voice: "Izzy Hell, you're so cool! You're my best friend! I just love how you make all the fascist Proud Boys and Kiwis quake in their boots! I wish I could be a badass Antifa super soldier, just like you! You're so cool!"
Phil in his normal voice: "Meow."