Aikidoka seem to be very upset about sparring. Sparring can be goood. It makes you strong and fast!
Training makes you strong and fast too.
If you're trained by a good teacher, you'll know which of your techniques will work for you "on the street."
I don't think "sparring" would give much that you wouldn't get from normal randori/jyu waza training. Although I can see how people I know would end up using awful bad technique which would be bad for their aikido in the long run. If you told me I was going to get mugged and gave me the choice, I'd personally take three hours of Kihon Gi over a month of "sparring."
Actually, I don't really see what's meant to set "sparring" apart here.