All other issues aside, his presence at his grandson's bar mitzvah would have turned the simchah into a circus, and completely shifted the focus away from the young man. There are many reasons why someone may not be able to attend a bar mitzvah. Keeping the peace is one. There is no shame here for Goldstone or the community that made this decision.
Chief suspect in Bangkok bombing case arrested (dpa)
from the article: Report: Zionist group bans Goldstone from grandson's bar mitzvah