Why whether or not one eats meat is not a "personal choice"

Sometimes non-vegans say that vegans shouldn't try to convince others to go vegan, and that "eating meat is a personal choice" that vegans should respect. But is eating animals really a "personal choice"?
I don't think it is. Here's why...
To begin, let's define "personal choice". In this context, a personal choice is a decision that does not harm or seriously affect anyone else, so the individual making the choice has the right to do as they wish, without anyone else intervening.
But eating animals-- and supporting the cruel and exploitative animal industries in general-- does harm others. It harms the animals. Animal agriculture is responsible for the imprisonment, torture, exploitation, and murder of billions of animals every year.
Whether you are a vegan or a non-vegan is technically a choice, but it is not at all personal. It affects others. For this reason, although I respect individuals who eat meat, I do not have patience for the choice to eat meat. I don't try to aggressively push veganism on people, because I respect the personal space of others. However, when people tell me that they eat meat, I don't simply smile and shrug and say "it's a personal choice", either. Instead, I politely mention that veganism isn't as hard as many people make it out to be, and then let them change the subject if they want to. If they do want to engage in conversation about veganism, I am all too happy to talk about it, though!