Though out history and still even, today, in some places. When we are all perfectly normal.
Well, I'm not part of that 'we', but used to be... And I'd question the veracity of that statement. 'All' is a dangerous thing to claim, when talking about groups of people.
I would argue that many Pagans resemble normality (leaving aside judgements as to whether they ARE, and what normal IS), and many do not.
AS to why I would regard many Pagans as wierd (the bad kind. Not the kind Im secretly fond of)... I've encountered Pagans online who thought everything that happened to them was a message from the gods - patterns of rubbish on the street, collections of animals found naturally in the environment, etc. Some of these people needed an omen before they could make a decision. There were people who were convinced they'd been cursed, because something bad happened to them. People who thought they were half demon, or whatever.
And given the slide I've seen these claims and behaviours get at times, yes I do often assume that a Pagan is going to be wierd. And thats despite having considered myself Pagan in the past.