Just in case you aren't aware of this, getting Paganism capitalized like every other religion has been a longstanding battle by the community as well as academics who study the movement for... unfortunately, literal decades. With no results. That's not some trivial thing, some innocent mistake. Capitalization keeps getting sidelined to the point that I'm not sure what else to call it other than some combination of active discrimination and inexcusable ignorance. Many of us are more than tired of it; this wouldn't even be a question for any other religious demographic.Even if he was, the lack of capitalization of a proper noun seems quite the trivial thing to be offended by nowadays given much of the younger generations were apparently never shown the 'shift' key on their keyboard.
In some ways, the situation reminds me of misgendering. For the most part, if someone misgenders you at first it's really no big deal as it is likely unintentional even if it is a product of a culture that often fails to acknowledge or respect your existence. The moment someone consistently keeps misgendering you even after being corrected, that's basically your culture trying to erase you. That's not just offensive, it's actively hurtful and damaging. Personally, I consider misgendering to be more severe than failing to capitalize someone's religion, but they remind me of each other a bit.