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.

[1] http://vanderburg.org/old_pages/Tcl/war/0009.html

Think about JavaScript, which was added to browsers the following year, explicitly with the intent of being "just a tiny little scripting language." I'm not generally that much a fan of RMS but his counsel here seems pretty solid. As odd as JavaScript is, imagine trying to write the client-side code for gmail in Tcl.

He has both good and bad points.

He is correct in that Tcl's niche is too narrow to serve as a universal scripting language (though that, as John Ousterhout pointed out, wasn't really Tcl's goal to begin with).

But he was also mistaken (I think) in thinking that a universal scripting language would be both possible and a good idea.

In practice, needs and preferences are too diverse for one scripting language to serve them all equally well; also, language competition is a good idea.

The biggest problem that people had with Stallman's argument, I think, was that he was pushing the immature GEL/Guile as a replacement (and it would remain immature for years to come), while Tcl at the very least did its job well.