Why yes, but what are our principles exactly? I haven't read an actual definition as of yet, so I'll propose to define this as "a central idea to being a communist". Thusly, without a principle, you can't be considered a communist. I furthermore propose these principles, just for the sake of discussion:
1. A working class orientation: self-explainatory really, the working class is the only consistently revolutionary class that can change society.
2. Struggle: change can only be done by class struggle.
3. Solidarity: basic solidarity among all of the working class in the direct class struggle and unity in political organisation.
4. Internationalism: the logical extension of solidarity on an international scale, but also the realisation that the struggle against capitalism has to be international.
5. Socialism: our intermediate goal.
6. Revolution: the means to this goal.
7. Workers' democracy: without workers' control and management over society, socialism is doomed from the start.
If we then take these principles and look towards the SWP, they comply on all points besides the very first as they don't have a class orientation but a communalist outlook (which leads them to weird constructions such as RESPECT in which bourgeois muslims were also a member and their support of reactionary organisations such as Hamas and Hezbollah). Also, they don't comply consistently to principle 3 as was recently shown in the Lindsey strike and because their united front politics are always highly centralised in their favor.
So I agree, based on these proposed principles a merger with the SWP is not possible.