I suspect that abusive behavior of advisors of graduate students is not uncommon. I was abused as a graduate student. His distribution of technical work and authorship as well as his references, reflected primarily these personal affinities. The department must have explicit expectations for student performance.
Some students finish with work which barely meets a reasonable standard of scientific merit.
There is an inherent conflict of interest in allowing the thesis advisor to participate in either of these landmark decisions. I might not pass because of my advisor's feelings. Secondly, the conflict arises again in the thesis magnitude of thesis work. If a student is outstanding in the lab, the advisor may require more work to finish simply to support his own agenda. The institution has the absolute obligation to develop a sanction mechanism for advisors.