I can't imagine anyone who loudly snores does it deliberately. Many may not even realize! ( and as someone said, unless they've already done so should be checked by a sleep specialist for sleep apnea --BUT it is not the job of a fellow passenger to tell them that) I know when I fly overseas night flights I get on praying that there are no snorers. BUT if there are I just do my best. I am more annoyed by someone who takes off their shoes and dirty feet smell raises up all around ( since they CAN control that) than a snorer.

As said, you are on public transportation and need to deal with other public!