You must rename the validate.bat_REMOVE_ME to validate.bat.
Also note that you must use an instance document (this is said in the readme, but easily overlooked). Use, e.g., SDD-Test-Simple.xml - SDD.xsd will not work.
When validation was ok, the command line will say "Validation was successful!!" -- Note that looking into the errors.log file is confusing because that one will accumulate the messages, thus is will still say: validation failed (i.e. from the previous run).