#2. The attacker hates women

The motive behind the cowardly attack on Bret Hart seems to stem from the attackers frustrations with certain decisions that WWE has made, most notably, as evidenced by a series of tweets on Twitter, the decision for women to headline WrestleMania.
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As you can see from the tweets, the attacker is angry and threatening towards Vince McMahon and considers the Triple Threat Women's Main Event to be an 'abomination'. This seems to have spurred his attack on Bret Hart.
So the best way to deal with someone who feels so strongly about women being given the same spotlight as men after years of inequality that he will risk physical harm and jail time to make a statement is to have a woman kick their ass - enter Ronda Rousey. Although any woman on the roster will surely do the job!