It's been a long time since I've read Das Kapital. I'll try to get to it soon and amend my previous answer to address his specific comments, rather than deal in generalities. (I do believe that the criticism is valid, but I only remember the conclusion I came to and not the reasoning--so my claim should, I agree, be considered suspect.)

Specific criticisms are always better, so it's not unreasonable to hold me to the standard of presenting them. (However, if I'm arguing against general comments with other general comments, I at least am not doing worse than the original.)