I think that we will all respect that candidate IF he continues to campaign for stricter gun control laws (and campaigns without security).
He will be proving that he sincerely believes in his cause despite any negative personal experiences.
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This news reminds me of a somewhat similar situation. (I will be purposely vague in order not to hurt anyone's feelings.)
In the 1960s, Mr. X campaigned for the rights of group Y.
Years later (when this group had achieved much, thanks to people like Mr. X), he happened to be in an elevator when a young man of group Y roughed him up and robbed him.
When reporters asked him whether he regretted all his efforts in behalf that group, he replied ABSOLUTELY NOT!
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Whether or not we agree with someone's cause, we can respect him/her if s/he is truly sincere.