What is your definition of EVERY OTHER type of racing? If what you mean to say is ONE type of racing my SVTF will lose to a Mustang in is drag racing...then yes, you are correct.
And "slower" is relative...true, my car cannot accelerate from a stop as fast as a Mustang. A fact I do not deny. But I ( a so-so autox'er) driving my car, can most likely maintain a higher rate of speed on a course that involves turns much easier than you (I assume a non-autox'er) could in your Mustang. Thus my car could or would be faster.
I certainly acknowledge that the Mustang is a great car (having driven a 5.0 LX for 4 years) But the bottom line is, my sub 16K car is superior to a 30K Cobra 'Stang in many facets of motorsports, drag racing not being one of them. But in my experience having run up against Mustangs at several autocrosses I can say that whoping my car is not, whoping enough to turn faster times than Mustangs including Cobras (and other "faster" cars) it is.
After all, every one knows speed isn't only measured in a straight line, and if thats what slow car owners always say, then I guess I'm slow.

BTW- good kills in the original post.