Both halal and kosher meat have exemptions from otherwise legally binding standards on stunning animals before slaughter.
So if you want to boycott halal, then you also have to boycott kosher. Although at least where I am from, it's easier to forget about kosher because there isn't a big Jewish community in the area.
As someone else pointed out, there is actually debate within the muslim community about whether or not stunning fits in with halal. The fact is that most places don't mark "stunned" or "non stunned" halal meat, so yes, you are taking a risk if stunning is important to you.
I personally wouldn't buy halal meat, nor would I be happy shopping somewhere that sold predominately halal meat products. I'm not saying that it shouldn't be available at all - that's not fair on muslim communities. No matter how fucking stupid I consider it.
I don't consider this a double standard. There is a REASON why there are european directives about animals having to be stunned. Because out of the two - it is considered far more humane. I know if I was going to be killed I'd rather at least get knocked senseless first, rather than just having my throat slit in a wide eyed panic.
It's no more hypocritical than refusing to eat battery eggs because of the cruelty involved, but being okay with free range. It's no more hypocritical than being happy to eat duck, but not foie gras or veal.