| In most contexts, this concept, akin to a ten foot pole, is a theoretical distancing tool (ha ha) when dealing with unsavory people or situations.
Its most effective usage is when in reference to a person of dubious quality as follows:
"What's that girl with the boots on the cracker scale?"
"She's not on the cracker scale. In fact, I wouldn't touch her with somebody else's dick."
This is a curious construct, to say the least, because the likelihood of touching anything with one's own dick should be slim to none in most circumstances.
Further, the possibility that somebody else's dick would even be available for tasking as an object for touching other people is (hopefully) equally rare.
All of which nearly negates any potential applications of this remark, save its sheer absurdity, which is so copious that it aspires to heights far beyond ludicrous. This level of silliness makes for excellent conversation fodder and witty remarks, and thus validates somebody else's dick for inclusion in the vernacular. | 
