This news is ten years old. And it is safe to buy any bitcoins which is available for sale.
The concept of tainting coins is a centralization strategy which the government wants to use to control Bitcoin.

- Jay -

The U.S government control most of the money forfeited in the silk road and what they seized from James Zhong, and they have even started liquidating it ^[1], i guess they are no longer 'flagged' or 'tainted' now that it's the U.S government that's liquidating the funds and you're free to buy it  . The term flagged or tainted BTC is not part of the BTC network or protocol, it is from pro censorship institutions that want to spread their censorship to BTC.

[1] https://decrypt.co/125081/us-government-dumps-seized-silk-road-bitcoin

If these "flags" had any real meaning, what would happen with coins seized by the US government? They would have to destroy it and never sell it.
What happens when you buy these coins from the government, because many people bought seized coins on auctions?

Don't you have more serious things to worry about? Every single day some US dollars are used to buy drugs. Do you worry that you could get some of these and give your kid as lunch money?

I wouldn’t bother about it if I were you. Do you go to bed pondering over whether the cash you got today from the grocery store was previously obtained from a drug deal? No you don’t. Besides how are we supposed to know where the bitcoins have been anyway?? IMO as long as you bought those “tainted” bitcoins legally and can explain your source of income if need be, then you don’t have a problem with the authorities.

I think this is a problem bitcoin mixers solve. You can use a mixer to clean your bitcoins if you’re so worried about where they have been, you send the bitcoins to a mixer and they will come out sparkling clean.

But they sell Bitcoins back to market, right? And the all of a sudden the "tainted" or "unclean" Bitcoins become miraculously untainted 
Can't you see the hypocrisy of our Governments and Law enforcement chaps?
So what's your worry here?
The moment you start believing in their (Governments') stupid moves and positions. Then you are done. What would be the purpose to use or believe in Bitcoin any more?

Un rank AKA Jay said, it’s a news from 10years ago but then, am interested in this comment;

Can bitcoin be really destroyed? I don’t think it possible except you mean loosing the private key to its wallet as that would be the equivalent of not having it been transferred or used by any means.
So in what context were you implying this?

Still, you have a commodity in the market and not the blackmarket or its likes but this is the US government putting out some seized coins for reuse by selling it to willing buyers. There isn’t anything wrong in that. It’s just business and should you care about your privacy, you can take steps to mix coins before retrieving it to a safe wallet.

I think the authorities can blacklist the bitcoin addresses that have been linked to the criminal activity, and since the blockchain is a public ledger, everyone can see when and where the bitcoins from these wallets are being moved, this is how the government follows the trail to find where the money is going. They also have the power to ask centralized exchanges to cooperate with them and report any suspicious transactions from such addresses. Like I said before, using a mixer makes it difficult for anyone to track your bitcoin transactions.

No matter how old was the news as long as the private key is being kept, it can still dump the price of BTC if they're going to sell it all in one time. I saw an article that the US government move some BTC that they seized from Silkroad to Coinbase for almost 10000 BTC. So as long as the Btc will be transferred to an exchange, we have to expect that it would be sold. We should be worry for this? The thing is we have to find the those exact addresses so that we can monitor the movement.

Source:
https://finbold.com/1-billion-worth-of-silk-road-bitcoins-on-the-move-btc-dump-imminent.
https://twitter.com/PeckShieldAlert/status/1633331891347820544

Much of these were confiscated. The US government itself sold a portion of the seized coins, probably around 20%. Whoever bought them should feel safe despite the fact that those were coins involved in illegal transactions. The US government still has tens of thousands of Bitcoin in their possession. But they know better than throwing away these dirty coins. They hodl them. They will probably liquidate them when the price is good.

So don't believe in tainted or flagged coins. Be cautious, though. But know that Bitcoin is fungible. The US government's Bitcoin has equal value with anybody's Bitcoin.

I disagree and you should not make irresponsible statements like this especially if it can increase the risk of someone's funds in an exchange or a bank account being frozen or closed.

Anyone can argue that taint is not real, however, this certainly does not assure anyone that sending tainted coins to a centralized service will not cause us some problems.