Oh man! I'm sorry that happened to you.

I've had friends who've volunteered for crisis lines, I've never heard that they're not equipped to deal with a person with an SI history. Maybe it was just that individual person, and not the organization as a whole? (If it's just the person, they should have been professional and asked someone else to speak to you instead). I know SI is a taboo topic and is still misunderstood, but that's really sad that that happened to you.

Maybe call back another day and ask to speak to someone in charge and explain your situation and ask what their procedures/policies are for dealing with people with an SI history?