How do I approach this nicely?
Don't reply to a rejection. It's unprofessional and helps no one--least of all you. Replies often get lost in the process of sorting so the chances the original editor will see it are slim. If you have a legitimate question, such as querying a story idea or clarification on our guidelines or asking us what we're looking for, this blog would be an excellent place to ask us.
And especially, especially don't send us a snotty response to a rejection. Now, I am terrible with names, so I won't remember you if you sent us a snotty reply. (I can't speak for my fellow editors--Lesley seems to have one of those steel-trap minds, and Dave is a lawyer--take what significance from that as you will.) Also, our office is the Internet and various restaurants in Boulder, so we don't have a "black-balled" bulletin board. However, my experience is that a surly attitude often matches sub-par writing, so if you're angry with an editor, you might take a fresh look at your own writing. Might you instead be angry with yourself? Next to parenting, writing is the most difficult endeavour I've ever embarked upon, so you're not alone in your frustration.
That's not to say we don't reject wonderful writing. We do, often. I see good stories that are just not right for Electric Spec, and unfortunately my time is too limited to mention it during reading sessions. And, since I now seem to have reliable Internet service for the first time in months, I will be reading in the next few days! (In other words, any delays are mine, and not my illustrious fellow editors.)