It's pretty much the only line I draw. Bodily fluids don't trouble me, but scat is just a bridge too far. Sure it's gets involved in ass play and anal fucking, but as an incidental to be averted if possible or cleaned up afterwards. And I guess ass to mouth which is not my all time favourite, but I do it if my partner/s insist or it just happens in the heat of the moment, opens me up to scat, but again it's the cock I'm into, scat is just a consequence. Let's face it, it isn't pleasant, it isn't pretty, it's not great lube, it can be unhealthy and it makes a mess. What do you like about it? The sheer depravity, the limits conquered, the bravado? I get all those things. It's how I feel about DP and deep throating and fisting (that last one on the limit for me) and how deeply arousing they can be. Scat is just not in that category for me.