Running with a martingale is like getting married to a beautiful woman. Everything is great for a while, but as soon as she gets upset too many times in a row (and this can happen after months or years), she breaks up with you and takes all your money!
In demoing, I figure as long as you can guarantee that the EA will win more than it loses, does a martingale become a viable. Having said that, nobody can guarantee anything, and any EA can have a horror month, at any time.
I feel a little more comfortable about it by at least having some equity management going (so a failing martingale can't blow up the account), and optimizing the bot on a particular pair, on a particular timeframe, for over ten years -- despite how much the optimizing kills my computer for a few days.
In any case, one only need read the disclaimers for forex trading