I agree with you David, there is no rationalizing away these heinous acts of "continuicide."
I should point out that in DS, changing history IS possible. We just never get to see what all the history-changing in 1840 did to the present. So 1840 screwed up later eras? Fine, let's see it onscreen! It might be interesting.
Most of the post-1897 storylines are hard to get through for me. 1840 isn't, because of writing (that is, how the characters react to events and the dialogue), atmosphere, characterizations, and many fascinating events that happen early in the storyline. Therefore, I'm powerfully motivated to try to "save" 1840, even if just partly, rather than turning my back on it. That seems like throwing the baby out with the bathwater.