Just because it has the word "entertainer" doesn't mean it applies. The definition of entertainer isn't clarified on the website, but likely is in reference to people who are hired to sing/entertain (such as musicians, comedians and emcees).
The Massachusetts government calls it a "performer":
http://www.mass.gov/dor/docs/dor/publ/pdfs/performers.pdf
Phil records video of himself and licenses his copyright/likeness to a 3rd party company who places advertisements on said content and pays him "royalties" based upon this. This is most likely in no way considered to be an "entertainer".
For example if you made a DVD in Washington to which you held the copyright, but 90% of actual sales occurred outside of Washington then you wouldn't be liable for those in terms of tax. Replace DVD's which are "tangible goods" to Phil's online videos (which seem to be "intangible goods") and you can argue that almost none of the customer base is actually within Washington.
Another example might be if you were a musician hired to perform at a function, you are a person who is contracted to provide a "service". Because the function would likely be based in Washington by Washington-based company then you have taken advantage of being located within Washington and therefore you should pay the business tax.
If Phil provides no "service" to companies or customers located within Washington state, then he is deriving no benefit from being located in Washington state. Even technically speaking he is providing no actual service and rather mostly receiving royalties from copyrights that he owns (and yeah, we all know there's a lot of autism when it comes to Phil and copyright, but for the purposes of this discussion, he licenses out copyright he technically owns and receives royalty payments based upon this and not for providing a "service").
The law seems specifically written to exclude the outright sale of copyright (like if he sold the DSP "brand" in one transaction). As companies are "licensing" his copyright, it wouldn't technically be excluded.
This part of the Washington laws is probably the most relevant when it comes to "entertainer" that I could find:
http://apps.leg.wa.gov/wac/default.aspx?cite=458-20-211
>tfw they use an example which mentions "Helicopter, Inc."
Anyway, the important distinction is that an entertainer is contracted/hired to provide services, whereas Phil produces his own video content which he licenses. So I can't see it as being the same. A contractor/performer/entertainer would likely not hold any copyright entitlement to what they do, much less receive royalties from it from out of state sources.
Having said all that, even if the copyright/royalties argument got accepted by the government he'd still have to explain the Patreon income as well as Twich bits/cheers. As neither of these technically directly relate to his copyright and are digital tokens it'd be a nightmarish complex situation. Supposing the twitch bits/cheers/subs fell under "intangible goods" then Phil could argue they were consumed out of state in which case the Washington government may have no basis upon which to claim tax.
If it became too complex to show where Phil's "consumers" purchase/use his "intangible goods" then some of the previous shit I pasted shows that it'd fall to whichever state the company is that provides said income to Phil. So if Amazon/YouTube are not based in Washington, then he can tell them to fuck off.
