One thing which would put me off menstrual cunnillingus is knowing someone has to do the laundry, and getting blood out of clothes or bedsheets can be a bit of a faff if you don't do it straight away and it's dried, and it would bother me even if I weren't going to be the one doing the laundry. I know that none of that is to do with sex per se, but then external things can quite often affect how people feel about sex, whether it's directly relevant or not. And I think that is probably partly why menstruation seems dirty, because it quite often does create extra laundry, and laundry is about getting things clean. Also, I am of an age where reaching puberty and being taught about the facts of life coincided pretty much exactly with the mid-'80s and AIDS, and we were all taught about the dangers of bodily fluids and particularly blood, and while we may now know that AIDS hasn't been quite as apocalyptic as feared, I think we are all far more aware of the risks of blood-borne infections and so on. Or maybe it's just me. STIs are on the rise, after all.
If I were with someone whose medical history I knew and therefore had as clear an idea as anyone can that they were free of known infections, then I don't see there's much difference between blood and sexual bodily fluids, risk wise. However, it's one thing while there's comparatively light flow, but as I've got older and periods heavier, I can't imagine wanting anyone going down on me when I'm getting through a tampon+pad combination every hour or two, and expelling great clots (they are quite impressive in their way, but not a sexual way), and likewise, I wouldn't want to go down on someone bleeding that heavily. Besides, it often comes with quite a bit of pain and discomfort, and I wouldn't be in the mood anyway. And I can understand there are people who would go for it (After all, there are people who are into golden showers and stuff), but as much as I can accept it as a fact, I just don't understand it at all. But blood seems rather less dirty than some more extreme fetishes.
(That year working in a medical library has its legacy.)
I don't know - I have walked through the office with a tampon in my hand on many occasions. Not very overtly, I don't wave it around, but just in my hand with my door pass and mobile phone. I admit an element of this is working in a male-dominated work-place, and if it embarrasses any of them, it would make me smile a little, not least because many of them are in heterosexual marriages with children. But also, if I'm wearing a t-shirt, I don't necessarily have a sleeve to hide it up (I do usually have trouser pockets available, mind you.) I also reckon if I just do it and don't make a fuss - well, after some years, I'm not aware of anyone actually noticing.
Just musing - not sure I have a point at all...