The only NI party that side with the Tories are the unionists, and they want to stay with the Union, so the situation is not the same. The SNP have made it their stated aim to achieve independence for Scotland. They couldn't do it the honest, upfront way and so now they are seeking to do it in a backhanded way. More fool all those who voted no at the referendum if they vote for the SNP in the general election.
How is standing candidates in a general election "backhanded"