In general, I have no problems with babies crying on a plane, assuming the parent is doing everything they can to avoid having the crying baby. This means bringing provisions for feeding prior to and during the flight and in the case of young toddlers, something to keep them occupied.
For older children/toddlers (who are capable of communication other than crying), I have no patience for their misbehavior, whether it is crying, tantrums, kicking the seat in front of them (I always seem to get the seat in front of a misbehaving child). The parents need to be responsible by bringing sufficient toys/snacks to keep their kids happy and disciplining them when they act up.
Many years ago, my husband and I flew to Hawaii - we took a laptop with us and a bunch of DVDs so we could watch movies on the plane. Across the aisle from us, there were two kids (I'm guessing ages 3 and 5) who were having major meltdowns because their parents failed to bring any toys or stuff to keep them entertained (on a 6 hr flight!!! WTF!!). One of the movies we had was Monsters Inc which we started watching - halfway through the movie, I looked over and the kids were staring at the movie on our laptop, completely silent for the first time during the flight and remained that way for the duration of the movie.
In the end, I would much rather be sitting next to a screaming baby (my headphones sort of work like earplugs) than to be sitting next to someone with horrible BO. We have our fair share of hippies in Portland who don't believe in bathing or deordorant, so I am more afraid of getting stuck next to that than a baby.
