Should I still consider this person as an advisor? I was discussing some matters with a potential MSc thesis advisor. However, when I pointed out a mistake they had made, they kept on stubbornly denying it and just dismissed my claims. This annoyed me as I had spent a lot of time verifying that 
 it was in fact a mistake and building up strong evidence, and this professor didn't even seem to make an effort to listen to my arguments. In the end I had to give up because I was not making any progress. 

In your opinion, should I still consider this person as an advisor? The thesis will take up 2 semesters of work. I fear that if my advisor is not able to admit their own mistakes, this could seriously compromise my work. Should I interpret this episode as a red flag that tells me not to work with this person? Or is it possible that as time goes on they would start trusting me better and consequently be more willing to accept my remarks? Keep in mind that aside from what I just said, this person seemed the ideal advisor for me right now.
You might want to talk with people who worked with the person and try to understand if he tends to overlook remarks from others or situation spesific reasons led to this particular problem for you. You can not jujge someone with only one behaviour but I think you can not ignore it eather. I would say just try to learn more about the person.