Of course there are tainted coins. Try spending known Silk Road coins for instance.
There are a lot of paper money seized by the government. Aren't they in circulation? Or would you deny accepting paper money just because once they have been used by a terrorist or drug dealer? That's the same with Bitcoin. If you and everyone would deny accepting paper money just because the money have been used in drug dealing, paper money wouldn't exist. The same theory is getting a position in case of BTC, they are calling tainted BTC so at some point, people stop using BTC lol.
I found a reply from LoyceV which I really liked pretty much, I used to think same as you about BTC but it's not really the case.
There are no "bad" Bitcoins. Saying certain Bitcoins are "tainted" is an attack on Bitcoin, and it only exists if people believe it. Stop saying it, stop believing it.
I disagree with this analogy. When you pay with cash, the cashier just puts it in a box, they aren't put into an eternal immutable blockchain with all the details there to see, which would only require your dox attached to that transaction for a government to try to see what's up. Also everyone uses cash. If you have never had BTC in KYC exchanges, the gov does not have you as a "bitcoin person" on their records, so you don't want to be found using BTC to pay for stuff, specially since like I said before, there is a public blockchain that's immutable, they may start adding up amounts and wonder where it's coming from.
And if nothing happens who knows in X years you end up in trouble. This is the problem with BTC, its not fungible. As far as I know, promoting on sig campaigns is legal since it's just marketing, but not sure when the promotion is a mixer. I wonder how people are using their money there. From what I've seen they do nothing with it but hoard it. As far as P2P, I don't trust people in real life, you never know who you are meeting with, and Bisq doesn't solve anything as far as fiat transactions, you are risking it the moment you do a bank wire.
This depends on the level of investigation that may take place with you. If you was a "good citizen" and prepared your tax file, it is unusual for the authorities to conduct a deep analysis of the chain to find out where your money sources are. Also, payments from signature campaigns are less than $1,2000 annually, which is a small amount for anyone who wants to do an illegal activity.
Personally, I advise you to convert your bitcoin into cash and buy gift cards from the nearest store, or stop using Bitcoin until there is a clear legal framework for it (you will not have to pay taxes, and the law does not require a retroactive effect.)
But the gov hates BTC, and as far as payments from sig campaigns, im not sure about the legal implications of promoting a mixer. The activity is definitely legal, since it's marketing, advertisement of a service, however im not sure if they'll like you promote mixers. As a best practice I would avoid any problems, and by that I mean not showing up with these coins on either KYC exchanges or building using services that go along with your dox on each payment. Also if you have other sources of income, it all adds up for taxes.
And also, if in the future BTC goes to 100k+ and you have coins you haven't touched for years and you want to buy a house or whatever, you are going to need to show up with these coins in a bank etc, you will raise alarms and get audited, in this situation, you would need to disclose your coin history and they would see you sent it to Bitrefill to pay for stuff. I guess if you stick to small purchases you could claim you didn't need to have that money taxed prior usage for payments, but with BTC I just know these guys hate you by default for owning any of it.