I'm not a big fan of all in with a small pair. They play poorly when used in that fashion. While there is a good chance you will be 50/50 you are actually opening up yourself to a wide range.
For example, you have 55. If you get called by A7 you pretty much have a coin flip. If you had 88 or 99 you are a 70/30 favorite with the same A7 call. This is why KK is ranked so high in the strength chart.
When called by a pair, it is usually a bigger pair putting you 20/80. If you had a medium pair, 88,99,1010, you could get called by 55-77 making you a favorite.
3rd, you are always subject to a board with 2 pair. If the board is 1010, 77, the
odds of the villain not having a card larger than 55 is low.
Small pairs have their place, I personally don't want to put in all my chips with one if possible.