"Increasing hostility" means that the level of unfriendliness, aggression, or negative feelings between people or groups is getting higher or becoming worse over time. Full definition
But please, the ever increasing hostility toward one another because we do not all believe the same thing is getting out of hand. (religion.blogs.cnn.com)
However, more often the outcome is a breakdown in communication, with increased hostility and anger, as well as emotional isolation. (thelawcollaborative.com)
2010 I quit the ministry after years of struggle and frustration, as well as experiencing increasing hostility about my blog. (nakedpastor.com)