logic?

Now I am not a logician or a philosopher, but I know an argument that does not stand up when I see or hear it. I also know a person who is prepared to believe the impossible or the ludicrously improbable to suit their ideological purpose when I see one. There has been too much of this lately. Down with this sort of thing, say I. Example (admittedly from the deranged wing of the so-called left): Israel has denied licences to "Palestinian" fishermen to fish in the Dead Sea, thus depriving them of a livelihood and confirming Israel's status as an "apartheid state". There are people out there who actually believe this, and who have not been sectioned or otherwise dealt with by mental health services. There are no fish in the Dead Sea. Never have been. The clue is in the name, folks. The Dead Sea is so saline that it can support only certain microorganisms. Not fish. The Dead Sea is fed by the Jordan, and fish are carried into it from that river, but they die almost immediately. These are facts.

I remember a line from 'The Golden Notebook', the seminal political feminist novel by the late Doris Lessing, a great influence on me when I was young, where a woman in East Germany informs a (German) visitor from the West that " they [the West] have no consumer goods". She leaves, and he tells his (non-German) companion "That used to be an intelligent woman". So what is it that makes a consequence of the acquisition of ideological conviction a loss of the ability to think or argue rationally?

I was told by someone who when very young was tempted by the far-left political groupings of the 1980s in the UK that he was told by an activist, when there was a steep rise in the price of gold, that this would result in " armed workers' militias on factory gates". Er, no it wouldn't, my interlocutor knew. But the activist who told him so genuinely believed it. So this is not new. Doris Lessing was writing in the 1950s about communist activists and ideologues in the eastern bloc that she actually knew. The 1980s political activist really said that about the workers' militias (in Thatcher's Britain!), and really believed it. The "pro-Palestinian" ideologue condemning Israel for the Dead Sea meant what she said. None of these people are trying to fool anyone. They believe they know the truth, and they want others to know it too.

Is it possible to combat this? Has it ever been? I only ask.