Personally I don't think they have any room to bitch.
The burka is inherently associated with the wearer's intent to be 'modest'. That is the entire reason they go round dressed like ninjas, whilst everything about the (western) bikini is pretty much the opposite in intent, purpose and practice. To get the kit off as much as possible, let as much of the body out to play as is considered not to be indecent exposure (by us white western folk, that is to say), so a so-called 'burkini', is essentially them emulating that which they claim to despise and be disgusted by. They bitch about us being 'immodest' by their primitive, backwards world-view and then go and DO exactly what they are whining and kvetching about.
Its the height of hypocrisy if nothing else. That, and fucking ugly as sin. But most of all, that is some ugly fucking hypocrisy and double standards. If they are prepared to bitch us out, only to do that which they claim to hate. Fuck 'em. Fuck 'em diagonally right in the ass with a pointy stick. Fucking slimy hypocrites.