Stallman was criticising the lack of arrays etc in Tcl which stops it from being used for building complex applications. Tcl author John Ousterhout responded[1] to this by saying that Tcl is a mere glue language and not a replacement for C/C++ and we need both type of languages.
If you look at today's language landscape, you have langauges like C, C++, Java etc occupying the "serious" niche and languages like Python etc occupying the "glue" niche ( although sometimes these languages do exchange roles ). The "glue" languages that succeeded did have support for arrays etc.
I think both parties have been proven right, at least partially.