That would be bad. It's not what's happening.

What's happening is "update your security on the thing that you have already got security on, or else at least two of the most popular browsers will mark it as insecure; also, you will lose points in our search engine".

They are getting close to a monopoly in the browser market and a monopoly in the search market, so yes, this is exactly what's happening. You can pretend it's not a big deal because now they are using their power for good (I guess), but you don't know what they may do next.

I don't disagree with their existence being a near monopoly at this point.

That said, slippery slopes aren't usually the strongest places from which to wage an argument. We're not talking about what they might do next. We're talking about this specific instance.