Unless being a Secret Service agent negates their humanity, making them either more human or less human, then they have the same strengths and failings as other human beings, and are able of the highest ideals and the basest instincts applicable to people. This means that while they are brave people sworn to protect the office of the presidency, are well trained and definitely well selected, they are still humans which means out of a given sample there will be those who would do bad/stupid things. Being a SService agent, just like being a cop or a soldier or a priest, doesn’t make one immune to sin, stupidity and senseless behaviour.
It should, that's why these individuals are hand picked to protect the president of the U.S. It's one thing to expose one's self to contracting crabs or STD's via this alleged behavior as a businessman or tourist is likely to do but it's a totally different story when these individuals allow themselves to become susceptible to intelligence blackmail by foreign parties due to their actions.