Several months ago, Microsoft took a long, hard look at making a bid to acquire Slack, the chat and collaboration tool that had taken the world by storm.

But Microsoft co-founder Bill Gates and CEO Satya Nadella fought against the idea. According to reports, Gates felt the money would be better spent if Microsoft built its own Slack competitor from the ground up.

Fast forward to yesterday. Microsoft released its new tool, Teams, which a lot of people think could put Slack out of business.

As a sort of pre-emptive strike, Slack took out a full-page newspaper ad in The New York Times, written as an open letter to Microsoft. (Slack also published the letter on its official blog.)

There's only one problem:

The ad was amazingly bad.

We could pick out numerous reasons this is one of the worst advertising spends of all time.

Here are four:

1. It brings attention to the competition.

A quick glance at the Slack's ad tells you only one thing:

The name of its now chief competitor: Microsoft.

I'm all for respecting the competition. But paying big money to put your biggest rival's name in big, bold letters in one of the most widely read newspapers in the country, and bringing attention to the launch of its brand new simply ludicrous.

Put simply, Slack paid big bucks to advertise for its chief competitor.

2. It's arrogant.

Slack begins with congratulations extended to Microsoft, but follows that by saying: "We're genuinely excited to have some competition."

I wonder how Slack's other competitors feel about that--including HipChat, which recently lured Uber away as a client, reportedly because of HipChat's superior identity and security controls.

Slack goes on to lecture Microsoft on the "degree of thoughtfulness and craftsmanship" needed to "build products that allow for significant improvements in how people communicate."

That's right, Slack is giving advice to the company that began revolutionizing the software industry while Slack's founders were still in diapers.

3. It's passive aggressive.

Slack presents this ad under the guise of "friendly advice."

But then it takes digs at Microsoft with statements like "we know that playing nice with others isn't exactly your MO" and "this is harder than it looks."

Slack, did you have to go there?

4. It (unwittingly) makes a case for Microsoft.

Slack highlights that the "modern knowledge worker relies on dozens of different products for their daily work, and that...these critical business processes and workflows demand the best tools, regardless of vendor." For these reasons, Slack argues that "an open platform is essential."

But as The Verge points out:

Slack has done a wonderful job at integrating many services into its product, but this doesn't make it an open platform that people can contribute to freely. There are 750 apps in the Slack App Directory, but any of those could disappear at any point because Slack controls the keys. Nobody is expecting Microsoft to do anything different, as that's the key selling point of providing this software as a service to millions of customers, so it's odd to see Slack position itself as "open" in the sense of software.

In recent years, Microsoft has been working hard to sell its cloud services across platforms, and integrate better than it has in the past. The software juggernaut is also in a unique position, as IT departments across the world are already familiar with its tools and security features.

In other words, this argument only works in Microsoft's favor.

Truth is, I'm a Slack user, and I actually enjoy the product.

But like too many other companies, Slack has been drinking its own Kool-Aid for too long. It seems the company believes it's the greatest thing to come along in recent years, and that it's irreplaceable.

And that's a mistake.

"Slack is here to stay," the ad concludes.

Guess it's time to prove it.