Based on the definition “A person who opposes and rejects many of the conventional standards and customs of society, especially one who advocates extreme liberalism in sociopolitical attitudes and lifestyles” then yes, most Pagans are hippies. However, not all would take kindly to that label. They all have different attitudes and political stances. There’s no one label or definition that fits all of them.
As for activism, I suppose it is pretty common for Pagans to be more prone to activism than the general public, since they respect the earth and seek to protect it. However, there are plenty of Pagans that aren’t into activism at all. They will do what they can on an individual level, but not participate in large-scale activism.
There are plenty of Pagans who are distinctly non-hippie and consider the hippie movement too extreme. These are the Pagans who do wear black and tend to be of a darker, more practical mindset. Being Pagan does not make one a hippie, much like being a hippie does not make one a Pagan.
Pagans as a whole are likely to be outspoken about their beliefs and are willing to stand up for what they believe. They’re also likely to align with causes that help the planet. That said, one-size doesn’t fit all, and different people will fall into different places in the activist spectrum.
*Disclaimer: I no longer practice Paganism, but I’ve left these Pagan Myths articles active because I believe they’re still valuable in helping people to understand Paganism and reduce negative stereotypes.*