Picture a game using dice. To “roll the dice” is to take a chance. When you throw the dice you don’t know what you’ll get - it’s a game of chance. The catch the dice means that while the dice are in the air, you reach out and catch them with your hand before they land on the table. It means not taking a chance, like saying, no I’m not taking a chance on this. I’m going to take this situation into my own hands. A non-unionized worker takes a chance that their boss makes the right decisions for them. This man is saying he won’t take that chance because it’s so unlikely. You may know this already, but the grammar of “catch them dice” is not what they would teach you in school. It’s colloquial, or informal speech. To answer your question about why they are laughing - I think it’s because they’re being informal and friendly with each other, chatting and having a good time. The mood is light-hearted.