Aikido is an art that is not based on strength. One uses the other person's strenght against them instead of opposing it.
However for aikidoka to be effective at punching they need to pratice punches on a daily basis in order to be strong enough to have an effect on the opponent. Avoid the punches if you can but and dont hit if you can, but if you do punch and want to have an effect, train every day with punching as the bad guy is usually quite strong.
I hope I didnt upset everyone with my opinion.