Apologies for being boring but......
I find these sort of threads a bit frustrating - if you really want to find out about a group, you could amongst other things, read their press, go to their meetings or for the more old fashioned on Urban75 write to them. The only thing you'll learn about the Spartacists, SEP or whoever on here is that they are 'mad', 'splitters, a sect, nutters, some of them are 'nice', etc. - depending on who is writing the post. All of which echoes much of what the ruling class say about groups & individuals who aren't 'on message'.
None of these groups are mad, or for that matter a 'cult' in the accepted sense of the world - neither the Sparts or the SEP lock up their members people can and do very regularly leave. Rather, they all have their 'take' on the world which you can agree or disagree with. This doesn't mean that I have some democratic view of 'ideas' - all 'ideas' are not equal, some are wrong, and others downright dangerous - but you don't convince others by calling them 'nutters' you need to try and engage with them, don't you?
If you don't want to - why bother engaging with members of groups at all - afterall the vast majority of people don't.
Oh, and the SEP members I have met and discussed with - at the Sheffield No War but The Class War group in the early 00s & at a David North meeting in London last December - have been really 'nice'. Trotskyists are people too