See i kinda disagree with that notion. That is to say i dont know about the motivations of the people you describe, however i have used Zionism as a term to specifically point to Israeli expansionism, as i believe there is a strong philosophical argument to make that there is a "strong ideological core component of expansionism to the ideal of Zionism", and that furthermore Zionism can be scrutinized as an ideology for that reason irregardless that this does not need to have bearing on the wellbeing of people within Israel.
I do understand that some have a different impression of what Zionism means, and are as many describe here against the current expansionism. And i do understand it would be annoying to be attributed an ideal to which you dont subscribe simply because of how people differently interpret the term.
It is a semantics debate for sure, but perhaps its not completely fair that one would argue that "anyone arguing against the ideoligy of zionism, has malicious intentions we should attribute to it". Atleast in the thought that you would ascribe all of them to be racist. I would think that for some of them zionism exactly means that which many others dont agree with either for what regards Israeli policy's in particular to colonization.
The reason I think the term Zionist is meaningless, and I agree with the way @west didsblue and @Prestwichblue95 have laid out their argument, is that unless you a) ascertain the context of the post containing the word and b) ascertain the intensions of the poster, it's almost impossible to know exactly which precise definition in which they're using the term.
Lots of people do use in the way you describe it, the expansionist, settler ideology, but lots of people also use it as blanket term for Jews in general, but you also have lots of Jewish people who consider themselves Zionists but disagree with the eradication of the Palestinian state/people, and you have Jewish people who consider themselves Zionists and do agree with the eradication of the Palestinian state/people.
If everyone who uses this term means something slightly different to the everyone else, then the term loses its meaning in any kind of serious debate. Saying the Israeli government and the expansionist, settler ideology is probably far clearer, if that's what you're referring to when you say Zionist, and it doesn't result in tedious back and forths about what words mean and arguing over definitions. Because when you say Zionist, and when I say Zionist we probably aren't talking about the same thing. Using clearer language would go a long way in all of us actually hearing each other and then having meaningful discussions.