Black Friday has been "a thing" all my life, but it's become more extreme in the past couple of decades. Of course there is something off-putting about it, especially for Christians who are supposed to be put off by materialism (mammon worship).
There is nothing inherently wrong with it. All it is at it's core is a big day for retail, the start of the Christmas shopping season for them, and a day where they can capitalize on people being off of work and in the mood to get a start on their Christmas shopping. I don't blame the retailers for doing whatever they can do help their businesses.
What I think is the off-putting part is that it creates an environment that brings out the worst displays of greed and materialism (again, mammon worship) in many people. I think in the past 20 years people have become so open and brazen about their greed because we have reached a point where the sin of greed and mammon worship is no longer considered sinful by most people, including many or most who deem themselves to be Christians.
It becomes highlighted when you see disgusting displays of people becoming abusive and violent with each other to the point where people are physically assaulted or even killed. But even without that the way people behave like animals when they are in the lines and then running through the stores, all for what? For material possessions and to help themselves save money. That is pure material/mammon worship.
So in summary, one can go shopping on black Friday and try to get deals and things but do it in a manner that is pleasing to God (because it is good to be a good steward of what God has given you and to make wise decisions in spending). But it is the way so many go about it that is displeasing to God, especially for those who call themselves Christians but then turn around and behave like animals whose primary interest is in money and material things.
I don't participate in the sense that I will not be foolish about wasting my time on lines or fighting crowds. I may go shopping and try to get "deals" but only if it's convenient and easy; I will not become a money/possessions-crazed animal who will do abnormal things (much less offensive things) to get "deals" or things.
Of all people, Christians should know that they have a Heavenly Father who wants to give us good things and help us spend our money wisely. If we act prudently and pray to God for help we don't need Black Friday to get "deals" because we will always be able to get what we want in a good way, if it's God's Will. If it's not God's Will He will direct us that way, also.
But as a cultural phenomenon Black Friday has become something that is mostly pretty evil. It's not the retailers themselves who are to blame but rather the people who feed into the money-worship that the day fosters.