Unsure if this is a new feature with the recent snapshot; did some research about the issue or looking if it was a new feature, but found nothing relating to this issue.
Problem

In the recent snapshot (14w06b) wolves, in peaceful difficulty, do not attack the player when attacked by the player. Instead, the wolf attack will go up to the player and just stand besides the player, doing nothing.

Steps to reproduce

1. Spawn a wolf (be in peaceful difficulty)
2. Attack the wolf (in survival mode)

Other notes

The wolf, that has been attacked, will continue to follow the player. In other difficulties, the wolf will attack the player as expected. This also affects wolves in a pack (group) in peaceful difficulty. Wolves will still attack other mobs regardless of difficulty.

Attachments

2014-02-06_20.03.03 - Wolf, as described, not attacking player
2014-02-06_19.48.32 - Normal wolf
2014-02-06_19.48.34 - Wolf following player (peaceful mode)
2014-02-06_20.09.42 - Wolves not attacking player, as described