Perhaps predictably, the people complaining about this feel that it's a form of rent-seeking by incumbents, but none of them have bothered to consider the flip side of the equation which is that bad actors who falsely hold themselves out as licensed professionals can hurt would-be clients in two ways: by directly exploiting them for the cost of services which they are not licensed to provide, and by jeopardizing their longer-term interests in a way that might severely impact them in the future.
Obviously this gentleman is not running around trying to scam Oregonians into paying for cut-price engineering work. But publicly asserting that you are licensed to practice a profession without actually being so, especially when licensure is generally easy to obtain, creates the potential for public misunderstanding. The point of the fine is not to impose a serious financial penalty (hence the token amount of %500) but to draw the public's attention to the fact that anyone holding themselves out as an engineer needs to be licensed within the jurisdiction in which they are practicing - and practicing on your own behalf is still practicing and indeed widely considered by professionals as a kind of marketing.
Considering that the annual fee to practice as an engineer in Oregon is only $75, and that engineering is well established as a profession, I don't think his complaints have a whole lot of merit. Last time I looked engineers are required to take ethics classes as part of their education, and in many jurisdictions keeping ones certification up requires a certain number of hours spent in continuing education each year, same as in the medical and legal professions. If you're not actively practicing your profession then you have, legally speaking, retired and should not present yourself as being currently licensed.