Problem is, that physics is an experimental science.
Relativity is confirmed by an incredible number of experiments.
Taking (at random) a relatively recent one:
NASA Announces Results of Epic Space-Time Experiment
May 4, 2011: Einstein was right again. There is a space-time vortex
around Earth, and its shape precisely matches the predictions of
Einstein's theory of gravity.
Researchers confirmed these points at a press conference today at NASA
headquarters where they announced the long-awaited results of Gravity
Probe B (GP-B).
"The space-time around Earth appears to be distorted just as general
relativity predicts," says Stanford University physicist Francis
Everitt, principal investigator of the Gravity Probe B mission.
see
http://science.nasa.gov/science-news...011/04may_epic
What do you have to say to that mister?