DES MOINES — The Iowa Senate on Wednesday approved a bill that would deny high-tech companies future state and local tax breaks if they were found by a court to have illegally stifled speech or certain viewpoints on social media platforms.“The sad reality is that we have liberal executives in the Silicon Valley dictating what Iowans are going to be fed through social media platforms,” said Senate President Jake Chapman, R-Adel, lead sponsor of Senate File 580.The bill, approved on a 30-17 party-line vote, could impact hundreds of millions of dollars — more than $1 billion by one senator’s estimate — in state and local tax incentives for Big Tech corporations like Facebook, Google and Microsoft if a court finds they have violated the free speech rights of Iowans.Republicans who touted the bill — which now goes to the Iowa House — called it a strike against “tyrannical propagandists” who must be challenged, given that social media has become the modern town square.