Rigor of Functional testing required after applying a Tools patch.

I continually run into a bottleneck with my internal customers when I suggest that we apply a peopletools patch to our systems.  The users say that the do not have time to perform regression testing and subsequently we are not able to apply the Tools patch.  I have tried to explain that this is a Tools patch only and it should have no impact on the application functionality; however, I work within a culture where everything must be testing period.  There is a fine line.  I know this is a general question but can anyone else offer insight into the level