I would say that a large part of developing maturity is learning how to interact with other adults in a reasonable fashion. There's a wide variety of different expectations, depending on where you are, who you're interacting with, and why you're interacting with them, but there are also some basic principles that will apply almost anywhere, and several general scenarios that can appear in almost any context.
One of those scenarios is dealing with someone who is being rude and offensive. Ideally, one can ask such a person to not do it again, and they'd honor that request... unfortunately, there are a lot of people who actually like being offensive, and don't care enough about what others think to even try to modify their behavior.
There are two ways to deal with this problem: Tolerate the offensive behavior in order to continue interacting with the person in question, or refuse to interact with them until or unless they act better. It turns out that neither is necessarily more mature than the other - in fact, I would argue that knowing how much you can tolerate and being willing to say something when you've hit your limit is more mature than bottling any resulting frustration up until you explode.
And it is entirely reasonable, when disengaging isn't an option, to note that you have a problem and ask those around you to help. It turns out that demanding other people unilaterally solve problems not caused by them is sometimes a bit much to demand.
That brings us to the other half of the problem: the person who's acting out in the first place. Does anyone really want to tell me that that person is being reasonable and mature in refusing to show consideration for the people around them?
A lot of the people that act offensively will react poorly when called out on it, and attempt to argue that the offended party's lack of toleration is indicative of a lack of maturity (or even mental stability) on their part. The irony of asking other people to show maturity and consideration when they appear incapable of doing the same is apparently lost on them.
Also, it may be easier for bystanders to try and get the reasonable, mature person to show more maturity... but that doesn't make giving up on getting the complete asshole to show a minimal level of maturity the right thing to do. It's also rather inconsistent to then blame the mature person for deciding that showing more toleration is too hard and not doing it - they made the same decision those bystanders did; it's just that the most reasonable action to take differs depending on how one is involved.
In the end, while some consideration for inappropriate or offensive behavior is going to be required, it is also not mature to repeatedly engage in such behavior, nor is it reasonable to demand that only one party in any interaction shoulder the entire burden for being tolerant and mature.