After the first person gets hurt, and calls an injury lawyer with a story of "they told me to take the stairs" you may reconsider whether this is a bad argument.
Yes, anyone can sue over anything. No, you won't win a stairway lawsuit if the stairways are maintained and other alternatives exist. You are unlikely to find lawyers to represent you (at least not on contingency) if there's nothing wrong with the stairway. A good lawyer would advise you not to sue.
This is a bad argument because it assumes that lawsuits over injuries are always easy to win and costly. They aren't.
Here's a California slip and fall ambulance chaser laying out exactly these facts. [1]
I know it's likely stairs killed your grandma but give it a rest. As I stated in the beginning and gave facts/figures for, stairways are safe for most everyone. Just avoid them if you've been drinking or you're old.
