As someone who suffers from selective mutism, I feel like a lot of people don't have it can't understand how to communicate with someone who does or think that they maybe even don't care. So, let me give an easier way to look at it.
Think about cats, they show you affection by just hanging out with you. They may not be able to speak and say "I love you!" but they show their trust for you through things like bringing you dead mice and kneading their paws on you. They always think about you too, they get upset when you come home late and meow at you to pay attention after getting off work.
Now, I feel the need to say that I am NOT grouping people with selective mutism, or who are fully nonvocal in with animals. What I am saying is that animals can't talk, but they still love you and want to spend time with you. It's the same for people who can't talk, we have out own ways of showing affection, even if some of us hate physical touch we still have fun hanging out with our friends.
I sometimes struggle to talk to my parents because of selective mutism, and they're understanding. Usually we'll hang out and watch tv and if they ask me a question sometimes I'll just nod or shake my head, and they understand that doesn't mean I'm not showing affection. The fact that I go out of my way to find a way to communicate alone is a form of affection.
So please remember, just because people can't speak doesn't mean they aren't trying to communicate, and don't force them to speak if you can't understand them. They're trying really hard, it's just different for them than it is for neurotypical people is all.
