This is an interesting question with several possible answers. In simple terms, discrimination is the injustice or unfair treatment that someone suffers from because of who they are. However, the matter is way more complicated and involves different issues to be considered, such as the legal aspect. That is, some regulations specify the grounds of discrimination and if any unfair treatment does not meet one of these grounds, then the unfair treatment is not considered discrimination. Therefore, it is easier to illustrate with real-life examples. For example, treating women in a disadvantageous way just because they are women is discrimination while acting unjustly against poor people such as the ladies from the text ”On the Dirty Side” is not considered discrimination because it does not the legal requirements of the definition of the term.
Despite the unfairness that is loaded in the term, one should be cautious about how to act when we witness discrimination or encounter it through discriminatory behavior. In the case of the nightclub and the young man, I would not interfere and I would not say anything. This is because the t-shirt does not say anything about the person nor does the decision of the nightclub when they deny entrance.
I would even react in the same way in the second case because the matter involves the personal safety of the kid. However, there might be room for leaving a comment or a letter to the site manager referring to adopting safety standards that are acceptable even for disabled people.
In the third case, the matter is not discrimination because marketing involves certain and specified requirements by candidates and when one can not meet all requirements, it is almost natural that they would not qualify. Furthermore, there is no legal ground for discrimination because of how one looks like.
In the fourth case, it is easier to get involved in a discussion with the gym personnel. This is because gyms nowadays are well equipped with machines that would fit everyone. Therefore, there is no reason to deny entrance to the old lady. I would discuss with gym personnel about changing their mind and if it does not help, I would scale the issue and report it to the management.
The fifth case is not about discrimination but rather about impolite behavior and preconceptions by the bartender. The decision about having fun is up to my friend while preconceptions and generalizations are not acceptable. Therefore, I will ask for an apology and report the matter to the management of the restaurant.