'Silly' in this case is not meant to be insulting or demeaning. In english the word can mean stupid, but it is not intended as as such in this exchange. The player is trying to say that by saying he chose the wrong faction you were lightheartedly joking with him. Words only gain true meaning from the context and the meaning here has been lost in translation. As a native English speaker, if this was said to me I would understand that the player was not trying to insult me but engage in some lighthearted joking prior to the op. There is no insult intended in this at all.
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