The following applies to the domain name question and the tag line question:
There are several issues to consider in looking at these issues. First, whether they are legal to do. Second, whether the company about which you are commenting and which owns the trademarks is going to sue you anyway. Depending on who they are and what the marks are, the products are, and the impact you make, I could see the latter being quite likely even if you are acting within your rights. You should know that.
Recall that we have relatively strong free speech rights in the US based on the First Amendment, so certain parodies of trademarks may be permissible if they are not too directly tied to commercial use. Also, where your use is editorial or artistic to the extent that there is no “likelihood of confusion" then, you’re likely in okay shape as a court may use the First Amendment as a factor in considering infringement. Be aware: the less commercial your parody and site are, the less likely you will be liable for infringement or dilution. Parodies that involve commercial use of the mark likely be seen as infringing. So, if you’re selling t-shirts, for example, that is not going to work in your favor.
Regardless of whether you act within your rights, the other party very likely will take issue with your activities. Prepare for them to be (very) displeased and you’ll likely want to consult a lawyer somewhere down the line.
Please note that this information is for informational purposes only and is not legal advice and should not be construed as legal advice. Nothing herein is meant to create an attorney-client relationship.
This question was resolved long ago and the law is clear: Yes, it is lawful to create a protest site using a domain name that includes the trade name of the company so long as consumers are not likely to be confused by the domain name or the site into believing that the company owns the site or is in any way associated with or sponsors the site. Which is very unlikely if the site is truly one that protests the goings-on of the company.
NOTE 1: You likely forfeit, however, your First Amendment right to use that protest domain name if you use the site to generate income. So if you intend to include sponsored links or other advertising means on the site you certainly need seek the advise of intellectual property counsel.
As to whether you will subject yourself to a trademark infringement claim by the company for your use of a domain name like acmestinks.com I think not. The law has been settled for so long on this point that if you confine yourself to what historically has been deemed acceptable the company's attorneys cannot ethically initiate a complaint against you. There are A LOT of facts in play in a case such as this so before you publish the site you still should consult an intellectual property attorney.
NOTE 2: In order to guard against this very scenario, smart intellectual property counsel always advise their clients to register the ...sucks.com, .net, .org, versions of their client's trade name. I may now advise them to also register the ...stinks.com, .net, .org versions as well. Those domain names should be resolved to google.com or to any third party site (it should not be the company website).
I agree with my colleagues. It's legal, but still risky. if you poke a lion, even from behind the bars of a cage, it's still a lion. But it's true that if the "Acmestinks.com" domain name is available, you have the 1st Amendment right to register it, and to use the site to criticize Acme. It's also correct that any commercial aspect to your critical speech will expose you to a trademark infringement claim, especially if you offer products or services that compete with Acme's, and/or if Acme can credibly claim that consumers could be confused by your use of their mark.
You may also have the protections of state anit-SLAPP (Strategic Lawsuits Against Public Participation)laws if your state has them, if Acme sues you to inhibit your speech. An Anti-SLAPP response can be a shortcut to protracted litigation, but even the threat of losing an Anit-SLAPP motion and having to ypay your legal fees may not deter a company under attack, so tread carefully here and only with advice of counsel.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.