Why does Jerry say that Peter will get cancer of the mouth?

Jerry has only just sat next to Peter on a park bench before he starts talking to him without being prompted. The men are complete strangers and yet Jerry has no compunction whatsoever in addressing Peter in a somewhat brusque, presumptuous manner. When Peter prepares to light up his pipe, Jerry proceeds to give him a little lecture about the dangers of mouth cancer, which he thinks Peter will get from smoking.
Immediately, we're put on our guard by Jerry. His opening gambits in the conversation indicate what kind of person we're dealing with. Jerry is a rather peculiar individual, one of society's outcasts with a slightly weird outlook on life. A gay loner who lives in a run-down apartment, it's no wonder that Jerry appears a little strange, especially when we consider the era in which the play is set (the 1950s). In a decade of often stultifying conformity, Jerry's about as nonconformist as you can get.