Interpreting sexual assault as humorous perpetuates rape culture and promotes the message that there is nothing wrong with touching someone else's body without their permission and putting them in danger. This attitude is insensitive and disrespectful and shows a complete disregard for women's right to feel safe in public.
Read the open letter from Hollaback! Belfast and Hollaback! Dublin: http://belfast.ihollaback.org/2013/04/24/open-letter-to-ian-dempsey-24042013/.