My point was that if we (the solar system) were travelling as a considerable portion of the speed of light, then we would experience time dilation, which would significantly affect our observations of the external universe.
So... it's fine.
I mean, you're basically right; speed isn't absolute, and it's wrong to refer to your speed relative to the CMBR as 'absolute'.
...but, well... I think it's fair to say 'The speed of light is constant in all frames of reference, so why [insert question here]...' is a very fair, and common question. 'Everything is relative' isn't an answer, it's just a platitude.