This is a form of advertising, similar to all other advertisements on the web. Some people have issues with ads that play during YouTube videos, but can this type of advertising harm the credibility of that project which published ads? No.
You have a wrong interpretation of good advertising, try to send an unsolicited message here in Bitcointalk and you will get a tag, try to send a private promotional message on Facebook and you will be blocked, try to send unsolicited emails through Gmail and your emails will be reported as spam and your account reported.
When it comes to advertising there are ethics that should be followed and sending spam advertising is a big violation of the privacy of one's individuals.
You don't compare your spam promotion with Youtube because they have a platform to show ads and when you sign up to use YouTube you agree and have consented to show ads on your viewing experience, in your case, people who will receive your spam do not consent to your action.
On the contrary, it demonstrates that the project uses various advertising methods to showcase its products to the targeted community and people.
Targeted audiences are those who agreed to receive ads and promotional not surprising them with ads without their consent this is simply spamming, or unsolicited messages.
We will include your Telegram username in the private message ads so that users can connect with you. As a result, users can choose to establish contact with you or visit your website to utilize your product.
People easily lose their trust in projects that prefer a method of spamming to promote their project
the bottom line here is we have a law against spamming and respecting one's privacy and it ha a very stiff penalty.
Each separate email in violation of the CAN-SPAM Act is subject to penalties of up to $50,120, so non-compliance can be costly.
CAN-SPAM Act: A Compliance Guide for Businesshttps://en.wikipedia.org/wiki/CAN-SPAM_Act_of_2003