It's almost never a good idea to accuse someone of lying. Even if it's true,
the accusation only makes you look aggressive and antagonistic. If someone
says something that you think is untrue, point it out, but in a way that
assumes good faith.
For example: "Could you elaborate on how Windows is faster than GNU/Linux? My
experience tells me the opposite."
Also, you need to be open to the possibility that you may be wrong, or that
there may be some nuance which makes both you and the other person partially
correct. A Windows system can
