I think most of his supporters don't believe it. They know it's lies, just as if you catch their hand near your pocket, they'll say it's innocent.
I remember a piece about how many of the people who support Putin are in a culture where they think hard work is done by suckers, and their goal is to live as well as possible while doing as little as possible. We see it in the shamelessness of the Russian media and the apologists.
One weird thing I've noticed in conversations about Russia and Ukraine is how Russian apologists try to invent their own arguments rather than going with what the Russians claim. I remember Tucker Carlson on a podcast with Lex Friedman (which I recommend as an example of how platforming a bad person can allow them to show how gross and stupid they are) ignoring Putin's claims of denazification and focusing on arguments Russia wasn't making, which still wouldn't justify starting a war.
You and the guy from the UK may be talking past one another if you're looking at the willingness of some politicians to say gross things, and he's looking at legislation.