The TV stations did no "simply" cut off Trumps "speech" .. they actively corrected it, or tried to.
It would appear that 7 major stations all did the same , with only CNN and Fox showing the whole "speech"
As an example, MSNBC anchor Brian Williams actually said "'Here we are again in the unusual position of not only interrupting the president of the United States but correcting the president of the United States. There are no illegal votes that we know of, there has been no Trump victory that we know of.'
USA Today, editor-in-chief Nicole Carroll, "President Trump, without evidence, claimed the presidential election was corrupt and fraudulent. We stopped the livestream of his remarks early and have removed the video from all of our platforms. Our job is to spread truth not unfounded conspiracies."
A little research can find further examples of the networks explaining why they took the actions they did.... if they had let the "broadcast" go they would be accused of inciting/supporting false allegations ..
Damned if they do, damned if they don't ... all depends on which side you support ... and I've only seen rampant "Trumpophiles" complaining that he was not allowed to complete his rant. I only wish I had been watching one of the stations that pulled it, instead I had to suffer the whole 17 minutes from the whitehouse livestream .......
As for "freedom of speech" .. a far wiser man than I once said "with freedom comes responsibility" ..... something Trump most certainly does NOT understand .. and he was NOT stopped from saying anything .. its just that his comments were not forced down the throats of viewers ..... .. his "Freedom to speak" was still there ....