Scientists may have made mistakes in the past, what is "emotion" and if emotion is just one part of the brain (which lizards lack). Furthermore, having emotions is not necessarily same like humans emotions, anyways. My guess is probably lizards (and insects) do have emotions, but not same like humans emotions (although, what are the similarities and the differences, is a question that remains, and you would have to know what is the proper way to measure such a thing).

I am not saying that I am necessarily correct about any of this, but you should not be so certain them the other way either.