It would be good if you reread some of this because in your emotional reaction ...
It is a bit rich talking about an emotional response, coming from you who in your response to Jakswan fails to understand that the SNP were largely seen in a negative manner in rUK. That is clearly true, and not just from those who disagree with their overall politics. The negativity was multifaceted involving:
1. Small 'c' conservatives who passionately want the UK to stay together and therefore saw the SNP as a threat.
2. Hung parliament 'worriers' who saw the presence of the SNP holding the balance of power - a party they couldn't vote either for or against, as dangerous to the interests of people outside of Scotland, on the basis that the SNP are clearly partisan.
3. Centre-left pragmatists who recognised that the rise of the SNP was damaging to the prospects of their being a centre-left government in power after the election, on the basis that the largest party would always get the chance to form the government (and most likely the governing party would get first crack) - so for there to be a centre left government Labour would need to be the largest party in terms of votes.
So perhaps the only people favouring the SNP south of the border were tories (and they weren't going to vote Labour anyhow) who saw their rise (and possibly independence) as a way of ensuring right wing government in rUK. But many of those are also in category 1.
If Labour's approach toward the SNP had been problematic in rUK, then surely it would have been felt most clearly in Wales, with its own nationalist tendencies and greatest levels of 'affection' for the goals of the SNP. But it wasn't. The change in vote share in Wales was broadly in line with the overall change - no evidence of droves of people taking Labour's approach to the SNP negatively.