I too am of the opinion that the issue is more about Si than Fe. Sure, Fe is involved, but its role is secondary.
Fe wants to create interpersonal harmony, but Si is more responsible for the belief that said harmony must be achieved by adhering to social norms. It is Si that notices the similarities and difference between things, events, peoples, demographics, etc. Strong Si users tend to be uncomfortably hyperaware of the contrast between what they perceive in the world around them and their internal norms. SJs also have a habit of confusing norms with ideals.
The weaker Si of NPs, especially us INTPs, tends to be hyperaware of and bothered by similarities to unjustified norms instead of differences. Difference between norms and ideals are to us like differences between reality and norms are to SJs.
Also, the idea of appealing to the disgust caused by viewing said hard-core gay porn seems more like an immature Fi think than an Fe thing. We could very well be dealing with STJs rather than NFJs.