Turning off breaker is dangerous?

[Wemustrv]

So unless they are using very inexpensive breakers they are meant to be exercised to keep all the mechanisms free. These breakers if UL/ CSA listed are required to go through cycling tests for certification. These tests are done with a load on and with no load. For details you can look at UL 489 standard. Smaller 15 and 20 amp breakers can be switching duty rated which means they can be operated as a switch.