Let me put forth an opinion that others are free to trash or disagree with. And please, more experienced BDSM (mostly BD in my case) players correct me if I need to learn something. First, I'm a male switch who, among other kinks like rubber, etc., really loves enemas. And I love D/s play and have done a good deal of it with several partners (incl my ex-wife) who loved it, including enemas. When I am in my sub role or sub personality, I often am told by my Domme partner that I have to endure things like full rubber suits and butt plugs and enemas. Depending on how we choose to do things any particular night, I'm usually the long-suffering sub who knows I have to do what she says, but with a lot of moaning, groaning, pleading and questions like "why are you doing this" and "no Ma'am, please not an(other) enema tonight," or "how long do I have to hold this?" And we both love it, including when I switch and am "forcing" my now submissive GF to take her enema(s).
The way I've read this thread is assuming the Dom(me)s involved are only "forcing" their subs to take enemas because the subs are allowing it and either tolerating or thoroughly enjoying it, like I would if I were the sub. Other than this or a similar scenario, REALLY FORCING someone IRL to undergo something beyond their limits or that they have expressly forbidden (often called a "Hard Limit") is not acceptable and tantamount to assault and battery, real prosecutable crimes. Now when I am subbing, I frequently get my limits pushed so she does something bigger, longer, harder or faster than she's "forced" me to do before this, like increasing enema size or length of time I'm holding it while sweating under a rubber suit and giving her orgasms. But that's why, among other reasons, that we use a safeword I (sub) can use at any time to stop or at least pause the Domme from doing something I can't stand or won't allow. Now believe me, when I'm subbing and I hear her say "I might need you to stay in your rubber suit and hold that enema until tomorrow morning when you'll be giving me wake-up orgasms," it gets my attention, truly makes me wonder how much I can (and want to) take from her. But it's still voluntary on my part and my safeword is always available. Other subs and Dom(me) partners can find all kinds of ways to "force" the sub to either take an enema or whatever the Domme wants, but the safe word is law. Any other sort of really FORCED task or punishment, including not stopping if the safeword is used, can't be tolerated and may in fact end the D/s relationship right then and there.
Now all I need is a new kinky woman partner to love and play with.