You're just trying to start the Christine Forum's very first thread war, aren't ya?
As has been said, it was two different sets of circumstances.
Lindsey quit the band in 1987
after a tour was booked. Christine, on the other hand, made it clear from the outset that she wouldn't be touring after 1990, only recording with the band.
There were no expectations that Christine would tour... however, there were expectations that Lindsey would tour. So feelings were hurt, and folks (fans as well as his bandmates) felt letdown or "betrayed."
If Lindsey had given a firm "no" right from the start, and made it abundantly clear that he was not going to tour for the album, and if he hadn't allowed dates to be booked, then I'm sure it would have been completely different.
Yes, fans would have still been disappointed he left the band, just as they're greatly disappointed Christine has left, but there wouldn't be that vibe of "broken promises."
I'm not criticizing Lindsey in the least, and you're right, it was a very selfless thing he did by folding his solo album into 'Tango,' and giving up his time to tackle the producer/arranger duties. And as far as I'm concerned it's all water under the bridge, but since you're asking why there's a different reaction from many of the fans in regards to Lindsey not touring and Christine not touring, these are the reasons as I see them.
