"Age is high price to pay for maturity" ? Well age isn't always an indicator of maturity.

So yesterday was the first of the month and rent was due for me. My 80+ year old landlord was outback with his nephew (who now lives downstairs) busy doing something with his van so I didn't want to disturb him. So once he went inside the shop I just put the envelope in through the mail slot. Afterwards I heard him talking about how he noticed the envelope and then made a wise crack to his nephew saying "age is a high price to pay for maturity". Well honestly sir I was just trying to be courteous and it had nothing to do with being immature. I guess he thought that I was avoiding him or something. One could also say that older age isn't always synonymous with maturity or wisdom either. I've been nothing but nice to this guy and always paid my rent on time during the 11 years that I've been there. I don't think I deserved that remark at all and I feel like defending myself. There are several ways to go about it but I wouldn't do it in a condescending or overly offensive fashion. More like something understated, indirect and ambiguous delivered in an innocent and pleasant way. Or I could simply just be extra nice to him. It's not really a huge deal but I guess some people will jump to conclusions about others without considering other possibilities. Which can be more of a reflection of who they are rather than an accurate conclusion of someone else's intent behind their actions.