A party was thrown to 'celebrate' the 9/11 Memorial Museum

Many people seem outraged (extremely angry and upset) that various wealthy and famous people - including ex-Mayor Michael Bloomberg - had a party at the 9/11 Memorial Museum before its official opening.

A 'memorial' museum is a museum meant to help people remember something.  Basically this museum is meant to help people remember the terrorist attacks of September 11, 2001 in New York City and Washington D.C.

By the way, the verb 'to throw' is usually used with the noun 'party'.  i.e. They threw a party for their friend's birthday.  i.e.  Are you going to throw a party for your child's graduation?

Here is an article about the 'party':

http://www.nydailynews.com/new-york/9-11-museum-hosts-alcohol-fueled-party-night-opening-article-1.1800072

Vocabulary to help you understand the article:

remains of attack victims - this means parts of the bodies of those killed in the attacks. Apparently many people burned to death and their bodies turned into ashes which mixed with the dirt.  So they could not get all the 'remains' of the dead out of the area. To be honest with you, I'm not entirely sure why the remains of some of the victims are still there (I'm guessing). It could be that these 'remains' or body parts were left there intentionally or deliberately as part of the memorial function of the museum.

an alcohol fueled party - a party in which alcohol was served and in which people had a great deal of fun due to the alcoholic drinks

honchos - big shots, important people. Conde Nast is a publishing company.

VIP - very important person

first responders - firemen and police officers; so firemen and police officers were allowed to visit the museum before it opened, but some of them were refused entry because a party was being set up on that day.

a blowout dedication ceremony - this means they had lots and lots of fun

the eve - the night before

sacred - holy, of religious meaning

nibbled - to nibble something is to eat something very delicately; to take small bites

billed as - advertised as

on condition of anonymity - he didn't want anyone to know who he was

festive - party-like, fun

hor d'oeuvres - little chunks of food eaten before a main meal and usually eaten with one's hands

a gravesite - a place where the dead are buried

soiree - a party thrown in the evening where people get together informally to chat  

desecrated - if you desecrate something, you take something holy or religious and use it for a less meaningful purpose

picking up the tab - paying the costs

tourist site and shrine - a place for tourists to visit and a place to remember those who died in a respectful manner

an advocate - someone who speaks in favor of something or speaks to promote something

Shame on the museum! - the museum should feel shame or embarrassment due to its actions