Alas, "effect" is also a transitive verb: you can effect change, i.e. cause it to occur.

And "affect" is also a noun, although rarely used.

  affect: the conscious subjective aspect of an emotion considered apart from bodily
          changes; also : a set of observable manifestations of a
          subjectively experienced emotion
          <patients … showed perfectly normal reactions and affects — Oliver Sacks>

(http://www.merriam-webster.com/dictionary/affect)

But it's still a good rule of thumb.

At least this usage of affect carries a different pronunciation. The emphasis is on the first syllable here, rather than the second, making it SOUND like a different word than effect.

And alas, "affect" is also a noun.

http://en.wiktionary.org/wiki/affect#Noun

The requirement for your argument is that the original poster of this side topic understands the differentiation between a noun and a verb.

Otherwise your generalization is aptly put.