Stating surprise about another researcher in my talk I will be giving a talk in a research seminar in mathematics in a couple of weeks. During this talk, I'm planning to present one particular result of mine which shows that a certain method introduced by another researcher several years ago is quite limited. This limiting result is really simple and I cannot believe that this researcher did not notice when writing their paper. 

When presenting this work to my colleagues at my own department I expressed my surprise during the presentation quite bluntly. 

I cannot go into much detail but given the structure of the paper in question I cannot imagine that they were not aware of this fact at the moment of writing the paper. To me it rather seems that they omitted this limiting result to make their paper seem better.

How should I behave at the research seminar at a university I'm only visiting where I don't know the faculty that well? Can I also express my surprise there or would this be considered bad etiquette? Not sure if relevant, but some of the people there might know the researcher in question better than they know me.

Edit to address some comments/answers: First of all, thanks for all the helpful answers, they really give me a new point of view. Secondly, I wanted to mention that it was not my intention to criticise another researcher in public. I was (and am still) honestly surprised about both my result and the other researcher. I learned from the answers that others could misinterpret my intentions and will therefore only mention facts. Thanks for that!
Talk about the work. Stick to the facts.

Clearly and bluntly stating the limitations of a result is fine, but criticism of a researcher during a research talk is completely inappropriate.  Your expression of surprise could be taken as criticism of either the researcher's ethics or their competence, neither of which is appropriate to air in front of a research audience.

Whether the researcher is junior or senior is irrelevant.  Whether the researcher is known to your audience or not is irrelevant.  Criticism should be delivered privately.