It’s not about being polite, and it’s definitely not to make it easier on translators; if anyone tried to do that with English, we’d probably end up doing away with whole parts of the language!
The ‘would’ in that sentence is showing that it’s a possible thing that they could do if they chose to, if they were willing to:
...20 percent of heart disease deaths among American women could be averted if the highest consumers of processed meat were willing to cut down to the equivalent of less than a half strip of bacon a day
Keep in mind, however, that there’s another way to use ‘would’ in an if clause:
...If the highest consumers of processed meat would eat the equivalent of less than a half strip of bacon a day, 20 percent of heart disease deaths among American women could be averted
In this if clause, the ‘would’ says that ‘if the consumers ate [did eat]the equivalent, then 20 percent of heart diseases deaths could be averted’, whereas the other one says that ‘if the consumers were willing to eat the equivalent, then 20 percent of heart disease deaths could be averted’.
Hope that helps!