As I see it, there are three sides to this, and in all situations one’s personal Rav should be consulted:
1) Lowering an existing standard of hiddur: for example, if you usually hold by a certain standard of kashrus, but are eating at your grandparents home, who hold a lighter standard (that is still a basic level of kosher). In my experience, most rabbanim have advised me that the mitzvos of kibbud and ahavas yisrael outweigh personal considerations (hiddurim).
2) Changing accepted standards of conduct to a hallachikly questionable mode of conduct for a good cause: Allowing casino nights for a tsedaka organization. I have heard some impressive rabbanim speak at these events, and others that are pashut fire against them. Again, ask your local rav.
3) Changing a social standard for a personal or social reason: For example, wearing biking clothes when biking, or running outdoors in more “sporty clothing”. Some communities tend to be more stringent, but this is generally perceived as less of a hallachik issue and more of a hashkfik one.
In all three cases, speak with a Rav. And please, in this time of sefirah, do not speak ill of others who have a psak different than your own.