Tis not "good argument" to appeal to that last bastion of credible information...the ultimate authority: Dictionary.com.
Just because a "
style of popular music that derives in part from blues and folk music and is marked by a heavily accented beat and a simple, repetitive phrase structure" exists, does not in and of itself make it rock. Sorry. By that definition, I could beat on a tin can after my tone deaf ears listen to Robert Cray and Bob Dylan...thus influencing my tin can beating...and as long as I thump in a "heavily accented beat and a simple, repetitive phrase structure" by your definition, my tin can beating is now "Rock." Woe to those that appeal to a false higher authority.