I have not heard of anyone being terminated for delays, this is assuming that they where correct in the reasons they took they delays. The vast majority of delays I have taken have been beyond my control, mechanical, loading ( a whole variety here from late packages, broken loading equipment, start carts that quit,etc) , weather, atc, etc. Had a few occurence in the past about deicing when the gateway was not prepared for the event.
The rule is follow the rules, if it doesn't make sense for the company to want something done don't do it, if its a grey area don't go there, if you don't like or agree with a rule or policy involve the union to get it changed or have back up when you draw a line in the sand. If its illegal or marginal don't do it, if you are thinking I can get away with this keep in mind that the company tracks everything. The place lives on Industrial Engineering.