I Don't "Fear" diversity either but I do have a low tolerance for criminal activity especially in tax funded public places. Listen to the online Enumclaw police scanner and you will hear the police reporting from the library on a regular basis dealing with mostly kids and many times it's open drug use / dealing,  thefts from vehicles etc.
 I have no problem with people who are homeless and underprivileged and I have volunteered in the past helping people of all kinds. I do not think the library is an appropriate place for people to engage in criminal or otherwise questionable activities. Remember when an 11 year old girl was sexually assaulted by a previously convicted child molester? STORY HERE --->  http://www.seattletimes.com/news/man-held-after-girl-11-reports-being-molested-at-enumclaw-library/
Again, I am not saying EVERY homeless person or teenagers gathering ( I was one once too) are bad and causing problems but I do think enforcing the law is not necessarily a bad thing.