Religion is a powerful thing. Individual faiths build up traditions, customs, writings, and a history that people get pretty darn attached to. In Acts, the disciples are proud of their Jewish heritage, but also trying to get people to see those old traditions in a new way. They believe that scripture predicted that Jesus would come and be the Messiah. They also think that it's cool for Gentiles to get in on the action and (while they're at it) not follow the whole Torah. It's not a popular idea. Old traditions die hard.
Questions About Tradition
Why do the past and tradition have such a hold on people sometimes?
In what ways do the followers of Jesus embrace tradition? How do they toss it aside or change it?
What are some traditions we hold really dear today? How do we react to people we see as trying to change them?