While all of this is true, I think it's only natural for beginners to ask such questions, and they need to get satisfactory answers if they're going to invest the time the long road takes. Dismiss the question out of hand, and you may have just lost a student.
For this reason, and also for the OP's own training, I think it's important to have a level-appropriate answer. Show the student what to expect on the road from "brand new beginner who can't even stand right" to "competent martial artist."
I really like that approach of "let's break it down togeter." One of my sempai who teaches a class was asked about rear bear hugs and he worked through it with the person. The "new" guy was fairly tough, something even folks with little or no formal training can certainly be, so it didn't look pretty. It was a good teachable moment for everybody, and in a number of ways!
I'm very recently appointed as the teacher for one of the classes in my dojo (a mere shodan) . and some of the new students told me that they're not very sure that Aikido really works without too much strength.. what would you do if you were told that?
I'm sure that my Aikido works (thanks to Sensei for teaching me well) so I was thinking of letting them attack me seriously, but I'm also afraid that they'll get hurt and it will become a big trouble for me.
Ask you sensei, since it's his or her dojo, however, the first thought that comes to mind is that how much strengths it takes depends on how well it's understood and that different people understand differently. Maybe point out that shodan means "first step." I would never ask someone to attack me "seriously," but I like the idea of working through questions as they arise.