For all you old folks, how big of a deal was check-raising back in the day?

Saw a guy lose two pots at a 1/3 game and as he was leaving the table, he muttered under his breath about players having "integrity." Is there or was there something inherently wrong with check-raising?

There are signs in my room that list a few basic rules such as No Smoking, etc. but one of those rules is that check-raising is permitted which makes me think it's a serious enough issue if it has to be posted.