That's a dishonest quote, you didn't include the context that was provided on why YVR considers it political.
> Additionally, YVR aims to be non-political and Open Media’s borderprivacy.ca website promotes an online petition with a political call-to-action directed towards government officials.
Not that I agree with YVRs decision not to allow the ad, but I find it hard to argue that a website including a petition and urging visitors to message the government about the issue to be "non-political."
Your point is technically correct (the best kind of correct), but consider that in the US, the IRS's rules for 501(c)3 organizations, for example, allow those organizations to advocate for political policies without jeopardizing their tax-exempt status, but not for or against candidates.
There is a legitimate argument to be made that policy advocacy is a different kind of "political" than what people generally take that term to mean.
EDIT: That said, I agree with the many other comments here that the tone of the ad in question was confrontational, counter-productive, and fear-mongering. They could perfectly well have made their — again, technically correct — point with a more constructive or informative tone.
I can personally be political but still inform people of their rights without being so. Now, if I asked for more rights that is probably a political statement.
> Now, if I asked for more rights that is probably a political statement.
That's literally what the ad in question is accused of doing. The link leads to a petition to ask the government for _more_ rights in regards to protection of privacy at the border.
If you read a bit further down, there was a political aspect to the advertisement:
> “Additionally, YVR aims to be non-political and Open Media’s borderprivacy.ca website promotes an online petition with a political call-to-action directed towards government officials.”
…telling people about their rights is non-political.