What is there to not get?
If you don't get why people think Charlie Gilmour is a complete waste of community time and resources, then probably none of us can explain it to you. But I'll try.
There are people in human societies that do things for others. They do these things in exchange for money. We call these jobs.
In order to get this money for performing these jobs, certain requirements or expectations must be met. Sometimes in the course of doing these jobs, a person might do something above and beyond these job requirements.
These actions aren't reimbursed or remunerated, and are considered an altruistic gift bestowed upon a third party, which can be an individual, a group, a nation or humanity as a whole. In most human societies, such gifts are considered special and most humans are grateful to receive them.
Such an action might simply be time, effort or resources, but to be considered special there should be some measure of sacrifice on the givers behalf. The more that is sacrificed by the giver, the more such actions are prized and valued by those that receive the benefits of the gift.
In most human societies, such gifts are held up to be positive moral or ethical (*) examples and the givers as positive role models for members of the society. Such is the esteem that societies have for some gifts that they will create lasting memorials to those gifts and those who sacrificed to give it.
You may have surmised that it is one such memorial that is at issue here. What most human beings find offensive about the actions of the drunk-selfish-selfentitled-rich-boy is that the memorial he chose to show his contempt for society on was one that the community built to honour and remember those who gave the gift of their lives to their society.
You see, what makes the gift of their lives so special is that as finite beings, human have very little time in which to think, experience, feel and explore their reality. To freely and voluntarily give up the rest of their existence for the benefit of their society is considered to be the ultimate sacrifice (especially as those who do so are often near the beginning of their lives). Given the permanent and irrevocable termination of the givers existence, no amount of money or other fringe benefits can recompense the givers for their sacrifice (**). Therefore the community of humans that recognise and appreciate the sacrifice gather to raise a memorial that remembers both the gift and the giver as a mark of solemn gratitude.
What made the matter worse in the eyes of most feeling human beings that weren't emotionally stunted, was that the memorial was not respected by a drunk-selfish-selfentitled-rich-boy that has given nothing of himself that wasn't piss and vomit.
[*] If required to, I can explain the difference in another lesson of How To Be A Human Being In Mixed Company.
[**] Such a determination does not take into account any non-corporeal afterlife that the giver may be entitled to or rewarded with, as the certainty that such a reward will be forthcoming is something that humans have yet to come to agreement over.