I think you're reading a lot into this post that isn't there. Is he angry or is he hurt? There's a hell of a difference.
The idea that letting him down easy, if the case is that he is hurt because she is his love interest and they have established that sort of relationship and now she is rejecting this form of love in what seems to be an insulting way, is going to make him into some degenerate is way off. There's nothing here that says his behavior IS unacceptable. It looks like it just isn't her taste. There's a massive difference between having differences in taste and purposely disrespecting someone else's boundaries. It may not be obvious to him that her tastes are so different when they are communicating through text and aren't seeing each other, or hearing tone of voice, etc.
You and Earl seem far too quick to be vilifying this person. Was he told clearly that she isn't interested in sex? Or does it seem like a normal thing, with them flirting and being each others love interests? It's not like this is a coworker or some stranger. She isn't responsible for his feelings, no, but she IS responsible for how she treats this man who is supposed to be her love interest, and in that scenario, you'd think that maybe she'd care about not hurting his feelings.
I forgot the exact word. He is offended. What he feels matters a little less than how he chooses to act on it, because that is the part that will directly impact LilyRoar herself. It is unacceptable if he reacts, well, unacceptably, but there is nothing here that indicates necessarily that he reacted acceptably, either. You and Siluil have posed options for if the latter is the case, and seeing none for the former, I posed options for if the former were the case, though my wording allowed for very little tentativeness, I apologise. If it were me, I would see this as a red flag (not meaning something is there, but that there is potential for negativity) when someone is so entitled that their offense is made very clear to the partner in a way that doesn't seem to be clearly resolved, or in a way where the partner keeps pushing regardless (he vented enough to make clear his offense without a hint of apology or compromise (at least it was not indicated so in the OP) after Lily had expressed their lack of preference for it). Accommodating that without calling out that entitlement is, in my opinion (and as I have posted it), not enough, and I posed a perspective that would provide an alternative to balance out what has been posted on this thread.
In my experience, too many women have been made to let the man off the hook too easy, and I always err on the side of a lot of caution (in favour of the woman) in these cases, as I have done here. In my opinion- and this is only my opinion, love should not let you be gentler or let someone off the hook lighter than you would have done otherwise, and thus the fact that they are mutual love interests is moot (again,
to me specifically) and not a reason to go any gentler on him, especially if it would accommodate or give lenience to things on ENFP's end at LilyRoar's cost, unilaterally, and without fair compromise, as I have indicated in my original response, albeit in fewer words. I gave my best advice, and it is something I would have done myself as well: confronted it gently but firmly, but as blatantly and honestly as possible. With my personality and my style of doing things, I consider it a lack of respect to butter up what I say just to make someone feel better. If I were the other person, I'd want that honesty, and Lily is free to take the advice and use it in accordance to how she usually conducts herself in these matters and in her dating life and as what suits her relationship with this man in particular.
Just because you don't understand people wanting, enjoying, and bonding through sex doesn't mean this man is "over-sexting" and it could be completely normal for him to be hurt and offended by being led on and then coldly rejected, if that is the case. Clearly, we don't know all details here. But as someone who shares a similar type to ENFP, I would be hurt if my love interest flirted and led me to think they were interested in that sort of interaction only to then insult me and act as if they don't understand how/why it's important to me.
This is moot (again, to me personally). I would have reacted similarly had the 'sexting' had been replaced with anything else, but then I also know that I have been told anything between being harsh words and having high standards, but LilyRoar's standards are what matter here, and she is free to toss my POV out if it does not reflect her situation or preferences. This relatively minor conflict is a good chance for LilyRoar to vet and assess how he reacts to being denied what he wants, and if LilyRoar is somehow, somewhy expected to cater and baby his feelings just to keep his affections, I would consider that a problem.
(And before I get called out for being hypocritical, if I were confronted with an equivalent scenario, I will respectfully stop and thank the lady for voicing her discomfort with me. Don't get me wrong, I know it can and likely will hurt, but I would
much rather handle that than rely on her willingness to be hurt just to spare my feelings. Not that that's what's happening here, but I am not saying this in favour of my own personal attitude towards sex, but in favour of my view of the very commonly unbalanced dynamics men and women have in dating.)
We do not know if LilyRoar led him on, and in this society too many men get away with blaming the woman for his own attractions. While my response may have been coloured by that, this was the assumption I was working with, not my own indifference to sex itself. If LilyRoar had indeed let him on, she can ratify that. If he had pushed her, this is a golden chance for LilyRoar to confront this with him in a way that is constructive towards the relationship itself. If he really is acting out of line, being called out would only benefit him as well.