I have to disagree with your premise that bucks have the ability to reason. Animals do not have the ability to reason, they react through learned behavior. Repetition. And they are driven, for the most part, by three things. Food, sex, and staying alive.
Your absolutely right that they sometimes act differently than other times, but the reason is not cognitive thinking, rather their reactions to certain stimulus likely differ due to their desires to obtain one of the formally listed big three. While Survival is normally foremost in an animal behaviors, the small window for breeding overcomes that natural behavior when the time arrives. What might seem like a normal reaction to a call most of the year may elicit a different response during the magical time of the year known as the rut. Their intense desire to breed overcomes almost all other behaviors including food and survival.
In fact the ability to rationalize would serve a buck well, but he simply doesn't possess it. Could he rationalize, he could assess the risks of disregarding his learned survival instincts for the joy of sex. He could make calculated decisions based on ever changing circumstances and come to conclusions that best serve his well being and his desires. Fortunately for us, we're able to take advantage of his inability to do so. That's why hunters love to hunt the rut. Because a rutting buck is anything but reasoned, he's guided by primal instincts.
Live to Hunt, Hunt to Live.