Edit: I stand corrected, the legislation will indeed harm tenements. I would suggest that arguing against legislation by showing a supporter's hypocrisy may not be the strongest approach. It is a tad fallacious after all.

Full disclosure, my incorrect original post:

Find a guy with dirt that supports protecting rent controlled units. Use that to attempt to discredit legislation that helps tenants.

If the best argument against protecting rental units is a weak Tu Quoque, then perhaps protecting duplex rentals is a good idea.