there currently doesn't seem to be a way to force players off of non-brush ladders (the hl2 ladders) without just briefly disabling the ladder entirely
seems like ExitLadder() doesn't fire outputs on the ladder entity, so maybe binding to SetLadder() is better, where ply:SetLadder(NULL) does the same thing but fires outputs
https://github.com/ValveSoftware/source-sdk-2013/blob/0d8dceea4310fde5706b3ce1c70609d72a38efdf/mp/src/game/shared/hl2/hl_gamemovement.cpp#L902-L910
there currently doesn't seem to be a way to force players off of non-brush ladders (the hl2 ladders) without just briefly disabling the ladder entirely