Selfishness is only a problem insofar as it actually causes legitimate problems for others. The amount of pollution any person generates throughout their life simply as a result of eating and defecating dwarfs any pollution generated by their cremated body when they die. It's negligible, and simply not worth talking about.

Also, please note that you can't meaningfully claim to speak for anyone other than for yourself. Even if you are a member of a certain population, you cannot claim to speak for the rest of that population - unless, perhaps, they have unanimously chosen for you to do so.