If you're discussing flu should you never bring up cancer for fear that you're equating it with flu?

So, for example, person A is in the middle of a discussion re. flu, (or whatever else) and someone says “Never mind flu, even cancer (or whatever else) ...”, and then person B says “So you’re comparing flu with cancer?” So, person B thinks person A is equating flu and cancer. Should no one bring up something a ton times worse thing in a discussion just so they can’t be misunderstood? What is the solution?