This article provides a pretty good breakdown of 9 reasons why people would be hostile towards furries.
The one that stood out to me most and was my first thought was:
Lack Of Understanding - As with anything new, there is a general lack of understanding of the furry community. The older generation has a more difficult time coming to terms with the furry lifestyle (…) Unfortunately, many people are not willing to give furries any patience. They hate them right away, without a second thought, just because they are different from them.