Why Does Guru Appear Angry

Thoughts carry energy.
The guru manifests an "angry appearance" to stop everyone's evil thoughts and negative energy. Otherwise, it will harm many living beings around.
Because everyone has received so many empowerments from the guru, they possess great energy. The negative energy emitted by each person not only affects the entire temple but also extends to a great distance in the surrounding area.
The video at http://youtu.be/tAvzsjcBtx8 clearly demonstrates the power of thoughts and words. A phrase carrying positive energy causes water molecules to exhibit a beautiful molecular structure. Conversely, insults alter the structure of water molecules, making them broken and incomplete.
Therefore, the Guru manifests the form of Yamantaka to balance and neutralize the negative energy emitted by everyone.