It's like in the experiment Ivan Pavlov did with salivating dogs. He'd conditioned them to salivate when they heard a bell because their brains expected food to come next. As sex educator Emily Nagoski says, "the dogs don't wanna eat the bells..." — it's just a paired stimulus & response.
As long as watching it doesn't impair other aspects of your life (for instance, you can't get other shit done b/c you're watching too much), you're probably fine. Just don't forget the impact of a REAL, FLESH & BLOOD partner. TONS of stimuli & sensory input there to pair ur arousal response around.