Wow. I thought I'd seen almost everything.
While everyone's poop does smell...well, I'm a big fan of probiotics. I'll go out on alimb a bit here. I think it makes a big difference. Simply put, we all rely on the bacteria in our gut to digest our food. If that population gets out of whack, bad smells are just a symptom.
There are probiotic pills, there's also probiotic orange juice now, and just about any yogurt or yogurt drink is probiotic. (as well as some other foods) It may be possible to suggest one or the other without ever mentioning the odor issue. There are MANY reasons why adding probiotics to one's diet in a smart thing to do, so there are any number of angles you could take in suggesting them. Along with probiotics, adding more fiber in one's diet will help. Fiber doesn't have to mean bran muffins - fiber comes in many forms. Adding more fruits and veggies is a simple way - esp whole fruits and veggies as opposed to processed ones. Again, it isn't hard to find MANY reasons why this is a wise thing to do. REally, the fiber movement of the past suggested some really gross foods (and those horrid tasting fiber powder!

. ) That is no longer the case. There's lots of high fiber foods - like most Kashi brand products - that are rather tasty.
Easily enough, look for a good book onthe many benefits of various whole foods. There's a number competing books right now that are available along the lines of 100 best foods to eat, or 'what not to eat.' Once you read abot all the health benefits of fresh foods, and all the nasty things that processed foods do - including rotting in your gut and creating nasty smells, it's isn't hard to motivate yourself to do better.
Keep in mind certain medications will kill off healthy bacteria - so that may be part of the issue - but then it's even MORE important to feed your gut healthy bacteria. Beyond that, a healthy gut vs. an unhealthy one - if that's the issue - will likely make the person feel a WHOLE lot better in a relatively short amount of time. It is also likely to increase one's lifespan. It won't eliminate all odors, but if someone has a particualy bad smelling odor, an unhealthy gut may be the issue. Beyond that - it is possible that unusually bad odors CAN be a symptom of other health issues.
Whew! Never though I'd post about this subject on the DIS....