Oversimplifying:

• Liberals say "do what you like". If you are liberal and choose not to do X, Y, and Z then you are not violating any of your espoused principles.
• Conservatives say "don't do X, Y, or Z". If you are conservative and choose to do X, Y, and Z then you are violating your espoused principles.

(I repeat, the above is an oversimplification, and in fact there are things most liberals say not to do and most conservatives don't object to.)