Nah, Raibow Dash just tackles Griffin and pins him to the ground in such a way that their genitalia are in tight contact, which, given that they're both, well, naked, is very awkward. Griffin is however committing hyperbole by calling it "rape". The rest of the Noodle Incident is quite true, and made for a Broken Pedestal on his side (he was disappointed that Pinkie broke her promise to laugh at him, and that RD would initiate violence over insufficient information) and a terrible impression on theirs (he acted like a jerk throughout the episode; man's got issues).