I hate all this 'you could say that of Hitler' stuff being bandied about. You could also say it of Florence Nightingale, Ghandi, Nelson Mandela, Emmeline Pankhurst, Rosa Parks etc. Do people really presume that 7 yo girls have particularly fascist tendencies?
Also, the promise has always been linked to the laws:
A Guide is honest, reliable and can be trusted.
A Guide is helpful and uses her time and abilities wisely.
A Guide faces challenge and learns from her experiences.
A Guide is a good friend and a sister to all Guides.
A Guide is polite and considerate.
A Guide respects all living things and takes care of the world around her.
The laws have always said a lot more about how you should act. Being true to yourself in conjunction with promising to keep the laws is far less dangerous than a belief that everyone should swear allegiance to a religion, whether or not they believe in it.
And before anyone says 'if you don't like it, don't join', the Guides have always been open to all, even during a time when that was actually quite controversial. Unfortunately, the Promise never matched that, partly because it was written during a time when it would be unusual to be open about being non-religious. S we had an organisation with a Promise that didn't match its ethos, this change is simply a long-overdue solution to that.