Are you going around planning terrorist attacks, vigilante violence, sabotaging critical infrastructure in groups or consistently materially supporting those who do? If so then yes.
If you aren't doing anything even close to this then no you wouldn't be.
You're missing the distinction between individual action (however abhorrent) and an actual terrorist organization. Organizations fund, cultivate, and organize attacks, as opposed to lone wolf terrorists, and therefore are much greater threats.
Timothy Mcveigh (and Terry Nichols) weren't members of a terrorist organization, but they were terrorists. Meanwhile, the ku klux klan has actual initiations, membership, and organizational structure. As do Isis and al qaida.
> or consistently materially supporting those who do
Yeah, I pay taxes.
And how large a percentage of those who identify with the umbrella term "antifa" do you think are actually members of violent terrorist cells?