You could be entirely correct - objectively.
Technically Allah and God may interchange in translation.
However, the point of the post is that subjectively allah refers to the muslim god (or, to God in arabic) and God is the god of the Christians. In a more obscure comparison - how would you interpret "By the Gods I did not shoot"?
Belief, propaganda, votes, are subjective issues, not based on one-for-one mechanical exchanges of equivalent elements.
By changing from allah to God, the author intentionally obscured the nature of the terrorist - making him appear to be a non-muslim to those reading the article.
I'm sure the author simply wanted to avoid profiling....no thoughts about misleading the public...not at all afraid that the party line might be smudged by mass murder...nothing like that, nah.
And with that, the argument is won. Thanks.