Not sure what got you thinking about Tisha B’av now, but yes, the Gemara seems to be telling us how trivial things got us into trouble when there was a Gezeira. I don’t don’t know about that grasshopper part but a party invitation is trivial enough.
We know that Sinas Chinom brought the Churban about, and we understand that the Sinas Chinom was by the Tzaddikim — since the Gemara says this after wondering why the Churban happened if we know them to be Tzaddikim, so the Tziddukim, Baysusim and Baryonim are not part of the formula. Therefore, knowing there was such a problem, we look into this incident and find such references even if that is not the focal point of this Sugya.