Personally, although I am very critical of the Brahma Kumarism and especially its leadership, I would admit and accept perfectly well that many people have strong, unexplainable experiences and visions whilst in connection with them. But it's a huge jump to then claim that such experiences must be "the god of all" or "the Supreme Soul" ... especially now that we know much more about the real history of the evolution of their thought and nature; the latter of which includes a tendency to constant over exaggeration and self-importance ... narcissism even.
Now we know that there was no god Shiva mentioned in their religion until after 1955 right through the period of their most intense psychic period.
Go to practically any New Age group and speak to followers of any New Age guru and they will say the same thing ... and they are telling the truth too. They really are seeing lights and so on. They just don't express the ultimate arrogance of claiming that it is "The" god of all. That's just the BKs and a bit of Lekhraj Kirpalani's personality ... the man who thought it was was god - or, indeed, "superior to god" (quote-unquote) - from 1932 to 1955. Prajapati God Brahma, Krishna incarnate.
I think the thing to do is look at the evidence and be extremely rational and logical about it all. To keep your feet on the ground.
Would the god of gods make false predictions, cajole and manipulate, make mistakes about such basic elements of history like not knowing the difference between Judaism and Islam, or that Islam and Muslim is the same religion?
Would the god of gods and the Father of humanity not know the population of his children, i.e. the population of the world ... which has continued to increase since he claimed it was 4.5 Billion, 5 Billion, 5.5 Billion etc?
Would the god of gods make false predictions about the End of the World?
Would the god of gods and his representatives on earth be honest and truthful and admit up to their mistakes?
Would the god of gods tolerate his representatives being dishonest and making false statements or exaggerations?
Would the god of gods make false promises of protection etc etc etc?
I think, very quickly, the answers that come to you would be no, no, no ... no, it would not be possible.
So, yes, all sort of weird and wonderful things happen in the BKWSU ... but, no, those do not add up to "god".
Then there come the problems within The Knowledge itself, e.g.
The Murlis say you cannot see the soul ... so what are they seeing?
The Murlis say god comes in an incognito form ... that you cannot tell when he comes , goes or does not ... that he does not "mount a virgin" (to use that wonder old phrase they used to teach), so how can he come in Gulzar (unless Gulzar is not a virgin)?
Etc etc etc.
I think for many of the Hindus, BKism is easy to accept because they are already enculturated into a religion in which gods are tricky, lustful, passionate thieves ... e.g. Krishna. A religious background were the gods are amoral allows the god of the BKs to be amoral. They'd expect it! God can be or do anything and then make it good afterwards! Even the whole idea of "god testing" by making false predictions comes not from Hinduism.
Then, I think we should view BKism from the point of view of other philosophical or spiritual paths and see how they would see it ... e.g. Christianity, Islam and Buddhism. What would their view of the BKs and their god spirit be?
Therefore, I think what one has to do is not listen to what they say, but look at what they have done and decide how Godly it appears.
Had the BKs just claimed that Lekhraj Kirpalani was some kind of spiritual master and had ascended to the next spiritual world where he remained working from to expand his religion ... then I would not see so much wrong with BKism. Lekhraj Kirpalani is their god, fine, Lekhraj Kirpalani probably is more accomplished as a human being than most of his followers and perhaps he can guide them from a world beyond ... why not?
But to make such an extra-ordinary as godhood requires extra-ordinary evidence and I don't see it with the BKs.
In fact, I see the opposite. They are gauche and have fairly low brow or bad taste; they are materialistic and power hungry; they are manipulative and constantly dishonest; they are conscienceless, and even insensitive social climbers who would even turn up at some family's parents' funeral in order to promote their cult ... does that all sound "Godly" to you?
If that is your god, you are welcome to keep him. If I had a god, he would be much cooler and wiser.
... and life goes on perfectly well without any thought of god or desires for sparkling lights.
I think one of the most insightful things ever said about BapDada here was by an Indian Brother who pointed out that the BK "God" had a lower middle class (not very well educated) Hindi accent ... and that just about says it all for me. The same apparently is true for Om Radhe. Apparently her speeches were really quite rough and simple (someone else, a native speaking, will have to comment on that).