A rumor dies when it reaches someone who won’t pass it on. Be the dead end.

Rumours are not strong, they are just fast. Each one survives only because every person it reaches passes it to two more, so the whole thing depends on nobody breaking the chain. That makes one refusal unusually powerful, because the version that stops at you never reaches the fifteen people who would have heard it next. No confrontation is required for that.

When the next one arrives, just do not move it. You can say you would rather not, or say nothing and change the subject. Either way the line ends where you are standing.