Hey there. I think your standpoint is perfectly reasonable. Here is some info I found from parenting science.com:
"Smoking and the risk of SIDS
There is something about smoking that makes bed sharing very dangerous. Studies suggest that the odds of SIDS, or sudden infant death syndrome, are 16 times greater if babies who bed-share are also exposed to second-hand smoke. This pertains to both prenatal exposure--i.e., babies whose mothers smoked during pregnancy--and to postnatal exposure to household smoke (Horsley et al 2007).
Why the link? That’s not yet clear. Research suggests that babies who are exposed to smoke have more difficulty arousing from sleep, perhaps because smoke exposure changes the serotonin pathways of the brain (Kinney 2009). And when babies having difficulty arousing, they are at increased risk for SIDS.
But regardless of the mechanism, there is a consensus that smokers shouldn’t bed share, and that smoking can explain much of the elevated SIDS risk associated with bed sharing. In some studies, the risk of bed sharing became statistically insignificant after researchers controlled for maternal smoking (e.g., Scragg et al 1993; Blair et al 1999; McGarvey et al 2003)."
Good luck to you, the evidence is on your side