It sounds like they don't have enough different bikes in your size to let you really try out lots, and so they want to sell what they have. And being frustrated sounds like a reasonable reaction.

When I was trying out bikes, I went to all three shops in my town. The first two each had me try a bike, and that was pretty much it. The third had me try this bike, and then listened to my reaction, and had me try another. And then another. I went back and tried the first and another, and so forth. They had enough bikes in my size to let me try a steel bike, carbon, different levels of aluminum, men's sizing, women's sizing. They switched out seats so that I could use a women's specific seat with each.

And in the end, they sold me a bike that makes me smile every time I ride it.

I know it's really hard in smaller communities to find shops with enough bikes. I wish it were easier!