ZD,
Your examples actually proves the fallacy of that supposition.
If you would look at the comments about Cholov Yisroel, you would see that the overwhelming majority of comments were saying that there is no reason to be makpid, and there were responses explaining why it is a good reason to be makpid, however, I do not recall seeing anyone who is makpid putting down those who aren’t makpid, as were a goodly number of the comments by those who think you SHOULD NOT be makpid.
Huge difference.
Another similar case is if someone choses to use a specific hasgacha, there were some here who went off the deep end, to the extent that they would BAN an item, such as Twizzlers, if it had an additional level of hashgacha.
And most of those taking on additional chumras are not “veering” from the Torah, they base their chumrah on general halacha, they may be carrying it a bit further than you would. (Do not bring in Burka Women to try to prop your argument, the problem with some of their adopted extremism specifically contradicts other halacha) On the other hand, SOME of the meikilim cast aside normative halacha and search for any available possible kula even when adopting such a kula is in contradiction to other kulas.
In addition, schools of thought that specifically teach hereticsm (think Farber) are open to criticism lest there are those that would fall into their trap.
And, to specifically address bike riding, I do not understand how schools not letting children bike to school can create damage to the community, or any community at that.