Scientists are generally not considered a threat to power (unlike high-ranked officials). For example, Piotr Kapitsa had his arguments with Lavrentiy Beria and Stalin. Instead of death (delivered for much smaller insubordination) he was gifted a rifle:

"Beria summoned Kapitsa who amazingly refused him: “If you want to speak to me, then come to the Institute.” Beria ate humble pie and took a hunting rifle as a peace offering. But Kapitsa refused to help anymore."