The Torah writes that Dasan and Avirom were among those who Korach succeeded in recruiting to join in his rebellion against Moshe. Rashi tells us that Dasan and Avirom were from the tribe of Reuvein and they resided south of the Mishkan, adjacent to Korach and the sons of Kehos. He explains that it was Dasan and Avirom's close proximity to Korach which caused them to become embroiled in the argument; as Chazal state, "Woe unto the wicked and woe unto his neighbor."
Rav Wolbe (Shiurei Chumash) makes an interesting observation. Dasan and Avirom are by no means new faces in the Torah. They made their debut in Mitzrayim when they were fist fighting, and in response to Moshe's attempts to end their squabble they challenged him, "Who made you into a leader and judge over us? Will you kill us just as you killed the Egyptian?" From then on they only caused problems. They informed Pharaoh that Moshe killed the Egyptian thereby forcing Moshe to flee for his life. They blamed Moshe when the work in Egypt got more difficult; and they kept some of their mann overnight despite Moshe's explicit command not to leave over any mann till the morning. They were experts at picking fights, but nevertheless, Rashi tells us that if not for the fact that they were neighbors of Korach, they would not have joined Korach's argument with Moshe.
Rav Wolbe quotes the Gr"a, who writes that there are two types of yetzer hara with which every person must contend; one internal and one external. In comparison, the internal yetzer hara can be subdued with more ease than the external yetzer hara. Dasan and Avirom had the potential to instigate an argument, but it was potential that was borne out of their internal yetzer hara. In this instance, since that they had no personal gain they would have had the ability to overcome their yetzer hara. However, due to their close proximity to Korach, they observed his actions (i.e. an external yetzer hara) and the potential became a reality.
With this approach we can explain another pasuk. The Torah (Shelach15, 39) exhorts, "Do not follow your hearts and eyes after which you stray." Rashi explains that the eyes see, the heart covets and then the body sins. Shouldn't the Torah have written "Do not follow your eyes and hearts" since first the eyes see and only then does the heart covet? The answer is that there are definitely desires which materialize internally, but most people have the wherewithal to overcome these temptations. However, once the eyes perceive the temptation externally, this ignites the desires that would have otherwise lain dormant. As the pasuk states, the desires do begin in the heart, but it is only after the eyes see, that the heart covets to the point that it seduces the body to sin.
Overcoming our yetzer hara is not an easy task. Yet, not being careful with what we see, or not being cautious when it comes to friends and neighbors who could be a bad influence, can increase the difficulty many times over.