The present tense is defined by Merriam-Webster as:
the tense of a verb that expresses action or state in the present time
and is used of what occurs or is true at the time of speaking and of
what is habitual or characteristic or is always or necessarily true,
that is sometimes used to refer to action in the past, and that is
sometimes used for future events
"This stops/ends now" is related with the bold part above and it has nothing to do with any occurrence in the future especially considering the adverb now in your sentence.
If you rephrase it to "We have to stop/end this now." or "This has to be stopped/finished now", it will be easier to understand its meaning.
The example in your question is a good example of the present tense being used for future events. As you can see in the link, there are not many Engish verbs whose present tense is used to indicate futures, e.g., to begin, leave, start, arrive and finish, etc.