I was directed by @Fossilplants to this article, the penultimate paragraph of which suggests to me that Titchmarsh thinks in exactly the same derogatory way about certain pursuits as those he criticises.
He complains about Mary Beard's and Jeremy Clarkson's gardening comments but then, according to this article, derides other perfectly good pastimes – dominoes, bowls, crochet, patchwork quilting – in the same way as they do gardening.
Son’s girlfriend diagnosed with BPD