Is it a good idea to use cardamom in chili?
Cincinnati Chili often has cardamom, along with cinnamon and cocoa. Cardamom is used in savory and sweet foods all over the world, not just in India. 

If you have reason to want to try this particular recipe, then try the recipe as written. There are thousands of beloved recipes for all kinds of chili. There is no reason to say, "That one looks good, I'll do it just like that but omit a certain ingredient 'cause it makes me nervous." 

Your friend's advice is a bit odd to me because Garam Masala usually contains cardamom (sometimes black, green and brown)

My advice is to either try the recipe as written, or find another with which you're more comfortable.

Or come up with your own. There are no hard and fast rules when it comes to chili.

BTW, I love cardamom in savory. I make a Vietnamese Beef Noodle Soup (Pho) that I crave if I haven't had it for a while. It wouldn't be right without cardamom.