See RCW 64.34. You owe the HOA dues under the terms of your agreement with the association. Your dispute with them about their trespass would be an entirely different matter. In other words, if they sued you for the dues, they would win.
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The prior answer is correct, and there is case law squarely on point to this question. There is no right to "offset," and homeowners who have a dispute with their association are specifically NOT authorized to withhold payment of dues because of any such dispute.
If you don't pay your dues and the association takes legal action to collect, you will be held liable, and you'll have to pay their costs/fees.
Your best bet is to do small claims court when you are next in Washington. You can also hire a lawyer to send a demand letter and ask for attorneys' fees, but if that doesn't work, you'll be further in the hole because of those fees.
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