If the Viznitzer Rav had a problem with Rabbi Lau, he should have made them months ago. You dont make demands 2 weeks before an event.
There is much money at state now, the tickets were alot of money, there are people flying in for the event.
Not to mention Rabbi Lau and others flying in from Israel and expensive involved with That.
If as Getzel says, Rabbi lau was invited because of Shottenstein, then dont accept their money. If you are going to accept a large donation from someone , accept the terms that the money is given.