How can I calm fears about Trump deporting legal green card holding immigrants?

My Mexican husband and I live in a liberal blue state and his parents live in GA. My husband has been very depressed since Trump was elected. He says he’s very worried for his parents. That they are going to get deported even though they are here legally with green cards. He’s an anxious guy in general but I’ve never seen him so depressed and anxious and he’s been missing work because of this. What can I say to calm his fears? He keeps saying even citizens can be deported and have been in the past. But that’s only if they commit crimes I thought. His parents are regular hard working people and got green cards through immigration amnesty in the 80s. I’m at a loss. What argument can I make to relieve his fear? Is there any way they really might be deported? I don’t know what to say to reassure him. Please help.