Do you think these violent actions are justified??
Violent actions, no matter what the motivations, CANNOT be justified. No justification. None.
Buddha taught the virtues or message of Love, Compassion, Equanimity; not hatred, anger and violence.
Are you OK with these kind of vengeful mindset from Buddhists (more so from HH Dalai Lama's students)?
How can Buddhists "OK" with vengeful mindset?
That is out of the question. Vengeful mindset is, again, the direct opposite of Buddha's basic teachings of Love and Compassion.
How can it be OK? It is definitely NOT OK to seek revenge and this applies to both sides.
The are many other more peaceful ways to resolve this issue on the ban of Dorje Shugden practice. The Dalai Lama camp must agree to a peaceful solution. The world is watching, there is no other option but peaceful agreement.