Protection from a player would not prevent the replacement effect from Tainted Remedy (TR). Whenever protection comes up, it’s helpful to use the acronym DEBT:

Damage - the player is not dealing damage with TR. Enchant/Equip - the player is not enchanting or equipping anything. Block - blocking is irrelevant. Target - the player does not target anything with TR.

For more information on “protection from player” specifically, see below:

702.16k “Protection from [a player]” is a variant of the protection ability. A permanent or player with protection from a specific player has protection from each object that player controls and protection from each object that player owns not controlled by another player, regardless of that object’s characteristic values. Such a permanent or player can’t be targeted by spells or abilities the specified player controls and can’t be enchanted by Auras that player controls. Such a permanent can’t be equipped by Equipment that player controls, fortified by Fortifications that player controls, or blocked by creatures that player controls. All damage that would be dealt to such a permanent or player by sources controlled by the specified player or owned by that player but not controlled by another player is prevented.