For slippery slope to be a fallacy it has to be absurd or a very far reach. In this case, if I understand the argument, letting ID in class is supposed to end in unlimited proselytizing.
It is not hard to go there. ID is religious-based, no matter what the current sanitized propaganda is lately. You let ID be taught in its current religious, non-scientific state, you're proselytizing, telling a captive group of kids your religious beliefs are the correct ones.
Now once you start proselytizing your creation stories, other religions will want to also. There is ample independent evidence (one thing that helps slippery slope not be a fallacy) of other religions wanting the special treatment Christians get in this country, from displays next to the creche at city hall, to non-Christian prayers at city council meetings.
So, yes, there is a reasonable slippery slope from allowing ID to wide-scale religious proselytizing.
Your first paragraph is an assertion followed by a mischaracterization. Prove your assertion and correct the mischaracterization.
Your second paragraph begins with a useless statement followed by another assertion. You follow that with a further mischaracterization of the point plus a straw man argument. Two fallacies in one. You are on a roll.
Your third paragraph starts with a false conclusion based on the mischaracterization and strawman. You stuff that strawman with more straw. You seem to think that the mere display of a religious symbol is proselytizing. Well it is not. Neither is a person who prays. Someone passing out a pamphlet on their religion might be proselytizing.
You last statement is an unwarranted conclusion, but may be considered your opinion, which makes it as useful as your favorite bogeyman's opinion is to me, worthless.
No, the VAST amount of evidence is precisely the opposite. I’ve personally yet to see a single case where those proponents of ID are calling for BANNING evolution. They’ve merely wanted it ALONGSIDE evolution, and let people make up their own minds, rather they accept one over the other, both or neither.
What I have seen, repeatedly is exactly that from the godless left when it comes to ID though.
IN FACT one school merely wanted the students to know that there were books in the library addressing alternate theories to evolution were available ON THEIR TIME, and THAT too was banned, the books were removed...this is simple information that was to be available OUTSIDE of science class.
Not to mention, Christmas being banned from school calendars, crosses from town logos under attack (L.A., Las Cruces) little pre-schoolers having to sing ‘O Holiday Tree’ instead of ‘Oh Christmas Tree’ (again too offensive).
We’re LOSING freedoms for the false excuse given for fear of prostelytizing. Again, we did BETTER academically when God wasn’t attacked in schools.