Why do Jack/Kate/John believe Michael?

[lisarasu]

Hi,

I'm rewatching S2, trying to catch up before the new season and I can't remember how this is resolved.

WHen MIchael returns from the "Others", he tells Jack & co that they can overpower the Others, that they have only two guns and so on. Jack and Kate should realize he is lying because Kate was already captured by the Others once, knows that they dress up and all of them have seen how many guns these people have.
So why do they accept Michael's statement that the Others have only two guns? Is this explained further down the road?

[Jaystar™]

No it's never really explained I wonder why they didn't remember when Jack,Locke,Sawyer and Kate got there Guns taken.

[Brother Desmond]

If I remember correctly I think they do address this. Before they go off with Michael, Kate reminds Jack about what she found at the medical station, and that maybe the Others are just pretending to be less powerful than they really are.

Before hearing Sayid's theory, and Jack being Jack, decided to help Michael anyway. Probably because he felt guilty about leaving Michael when he was forced to lay his guns down. After Jack and Sayid formed their plan to ambush the Others Jack probably felt confident that with Sayid's plan they could take the Others, even though they were more of a threat than Michael made them out to be.