Fiancé doesn't care about safety of his child!

My fiancé wants a Jeep Wrangler and keeps saying "stop looking at crash tests that's bad" and won't say no to the fucking car. WE HAVE A 19 MONTH OLD SON. The crash rating is TERRIBLE. He is so hardheaded I can never get anything through his fucking brain. I know if he would actually listen to what I'm saying he would understand and not do it, but it goes in one ear and out the other. How do you get your SO's to listen to you? I'm in so many tears right now because I feel like he couldn't give 2 shits less about the safety of our child.☹️