To be fair you were quoting statistics for ranges (1000 meters IIRC) that were far beyond common, or even plausible combat ranges in which a Sherman would face a Panther. Just look at the career of Lafayette Pool (the greatest tank ace IMO because he accomplished a huge amount in only 81 days of combat). While that may have not been the crux of your argument, and he may have misrepresented it, the way you phrased your statement made it seem like you were evaluating combat effectiveness at absurd ranges.
Americans with relatively underpowered 75mm guns would have wanted this to be true. But it's not.
BRL Memo no. 798, "Data on World War II tank engagements involving the US Third and Fourth Armored Divisions", by D. C. Hardison, June 1954, is based on 86 tank vs. tank and tank vs. anti-tank engagements fought by the divisions mentioned. It gives the average ranges at which tanks were destroyed, in yards, as follows:
Allied tanks__Enemy tanks__Place
476____________N/A_______Vicinity Stollberg
959____________733_______Roer to Rhein
1000___________833_______Belgian Bulge
1260___________936_______Vicinity Arracourt
1116___________831_______Sarre
731____________915_______Relief of Bastogne
The overall mean casualty ranges are given as 946 yds for Allied and 893 yds for enemy tanks. The distribution of combat ranges was found to fit approximately to a Pearson
III distribution.
http://www.amazon.com/Data-World-War-Tank-Engagements/dp/1470079062
"Red Army Handbook 1939-1945", by S. J. Zaloga and L. S. Ness, 1998 (Alan Sutton, Thrupp) gives on page 179 a table of the ranges in metres at which Soviet tanks and assault guns were knocked out by 75mm and 88mm guns in 1943-44, as follows:
Range_______75mm gun_____88mm gun
100-200_______10.0%_________4.0%
200-400_______26.1%________14.0%
400-600_______33.5%________18.0%
600-800_______14.5%________31.2%
800-1000_______7.0%________13.5%
1000-1200______4.5%_________8.5%
1200-1400______3.6%_________7.6%
1400-1600______0.4%_________2.0%
1600-1800______0.4%_________0.7%
1800-2000______0.0%_________0.5%
The original has omitted the line for 600-800 metres, so I have calculated the entries for that line by subtracting the sum of each column from 100%.