I'd guess aggression would have a polarising affect, depending upon ingroup or outgroup affiliation.
Aggression from an member of your own group is directed at something important that you ought to take note of. Aggression from an outsider is possibly directed at you so something to be ignored (if not credible) or countered.
We really need some students to do some tests upon, or a better way of searching psych research than google.
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July Part 1