I suspect some of the more vicious answers come from a lonely place
There's several rational arguments you could use: MDMA is unlikely to cause cardiac arrest, or anything needing CPR. On the other hand, alcohol and painkillers could both require CPR use, if taken in excess. I would assume your boyfriend hasn't needed you to perform CPR on him, so what reason does he have for thinking you will need it?
But ti-for-tat arguing never really works in a relationship, and I'd wager his problem is more related to you going into the desert with a stranger WITHOUT HIM, then it is about you taking a pretty common drug.
The things you'd need if you were desertbound:
- Water and lots of it. More then you think you could need.
- Sunburn cream. Makes sense.
- A means of creating shade. Ie. a tent or the like
- First aid kit. Bit excessive, but why not?
- A sober person who can drive if needed.
- No alcohol.
If you take care of these things, then your boyfriend shouldn't be bothered. If he still is, you need to decide whether to respect his wishes or just do what you want to do.
Me and Miss Willow have disagreed on drugs a few times; so I try and ensure that she knows whats going on if I'm tripping (what drug, how much, etc.), but I also make sure that I'm not being the annoying tripped out idiot; I try and take myself to a place where I can sit outside in the backyard just chilling out...
But with MDMA, I used to pop around to her house, and she'd be chewing her face off with xtc-ness :D It didn't bother me, except that she would sometimes want to drive places (and usually I'd be fucked up too), so I would instigate a walk-about. You can't control your partner, and it would be shit if if you did, but you can try and be rational and safety-conscious.