Marius Joubert soft spear tackle

After seeing Morne Steyn get red carded for a spear tackle a couple of weeks ago, Marius Joubert was only yellow carded for this tackle a week later.
It was definitly not as dangerous as Steyns, but the question has to be asked - should it be a red card for any spear tackle, or is each tackle judged according to the severity of the impact?

It may have been a spear tackle, but it wasn't a "true" spear tackle, as Joel Stransky points out.

Both fans and players alike need consistancy from the refs and the IRB rulings. My feeling is that each tackle should be judged accordingly. Therefore, a yellow was sufficent here. Your thoughts?